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# Physics 17 Projectile Challenge

Do you like a challenge?

We are going to set up a slanted ramp leading to a level ramp ending at the edge of a table. When we release the ball at the top of the first ramp, it will accelerate as it comes down into the second ramp which will launch it out in an arc from the edge of the table until it hits the floor.

Where will the ball land on the floor? That’s the challenge. Can you calculate where the ball will land?

Question: Where will the ball land?

Materials:

Two ramps [one must be over a meter long]

Meter stick

Stopwatch

Pan 10 to 15 cm across

Ball

Procedure:

Mark out 1 m on the long ramp

Knowing the velocity of the ball is critical in your calculations. Using a 1 meter section is long enough so timing can be done but not so long the ball will slow down much due to friction.

Set up the long ramp level on the table top so it ends at the edge of the table

Set up the second ramp on a slant so the bottom end leads into the long ramp

The ramps are set up and appear straight. I found the ball itself would cause the ramps to shift a little. I didn’t tape the central part in place and should have.

Make sure both ramps are secured in place

Put a barrier at the edge end of the long ramp to stop the ball [a cloth will work]

Why stop the ball? So you won’t know where to put the bucket without calculating the distance using your measurements.

Mark a starting line near the top of the slanted ramp

Release the ball at the starting mark

Time how fast the ball goes over the marked meter in the long ramp

Repeat this at least three times or until each time is close to the others

Take the barrier out of the long ramp

Measure the distance from the edge of the long ramp to the floor in meters

Calculate the distance the ball will go before hitting the floor [See analysis]

Place your pan with a cloth or sand in it to keep the ball from bouncing where you think the ball will land [Make sure it is straight out from the ramp.]

Note: Be sure you measure from straight down from the edge of the ramp. Why?

Release your ball at the starting mark

If your ball does not land in your pan, try the challenge again

Observations:

Velocity times:

Timing a ball for one meter is difficult. It covers the meter in about half a second.

Distance to the floor:

Analysis:

You have two formulas to work with: d = vt and d = at2.

Remember a is due to gravity and is known to be 9.8 m/s2.

Look back at Physics Project 16 to see which formula tells you how the ball moves, forward or downward. Which values do you know?

Give it a try on your own.

If you have trouble:

When you measure the time it takes for your ball to travel one meter on the long ramp, you have the v for the first equation. The d will be how far the ball goes when it leaves the ramp which you don’t know yet. The time is how long the ball will be in the air when it leaves the second ramp which you also do not know yet.

The height from the edge of the ramp to the floor is the d in the second equation. You also know the a. Use a calculator to solve for t as you must find the square root.

Now you know the t for the first equation and can calculate the d.

Notice the jag in the ramp. I had to correct this then place my bucket to catch the ball.

Conclusions:

What I Found Out:

I will admit I do these Projects in a hurry and am often a bit careless in my measurements. That is a recipe for disaster in this challenge.

First problem: The ramps must line up in a straight line or the ball will wobble from side to side or even jump out of the ramp.

Second problem: Both releasing the ball and working the stopwatch. It helps a lot to work with a friend.

Third problem: Measuring the height at which the ball is released accurately if this is not the very top of the ramp. My first measurement was off by almost 2 cm. Also note this measurement is not to the top edge of the ramp but the place the ball is set.

Will the ball land in the bucket? It took several measurement corrections and calculations, but it finally did.

In case you haven’t figured it out by now, my ball missed my bucket for several tries. I redid my height measurement first. This helped. Then I retimed the ball and found I was off by over half a second.

My ball did finally land in the bucket.

# Physics 16 How Far Does a Projectile Go?

When a projectile such as a ball is tossed or thrown, we saw the ball has two big vectors. One is gravity pulling the ball downward. The other is the force pushing the ball forward.

Finding how far a projectile goes is influenced by both of these vectors. But how?

Try this experiment [a friend observing helps]: Stand still and drop a ball catching it on the first bounce. Do not throw it. Ask your friend the path the ball followed down and up.

A dropped ball goes straight down due to gravity then bounces straight up due to elasticity of the ball.

Next walk across the floor. As you walk, drop the ball and catch it on the first bounce. Ask your friend about the path this ball followed.

When you were standing still, the ball had to go straight down and up for you to catch it. When you were walking, if the ball dropped straight down and came straight up, you could not catch it because you were moving. The ball had to follow a curved or projectile pathway.

When you walk forward, you have momentum. Even when you just drop a ball, it has some of the momentum from you so ti follows a curved path down and up so you can catch it instead of passing it by.

This shows the two movements of a projectile, although influenced by each other, work independently. This is important for finding out how far a projectile will go.

Question: How far does a projectile go?

Materials:

Rubber ball

Meter stick

Stopwatch

Procedure:

Repeat dropping and catching the ball as you walk to be sure you are dropping the ball not dribbling it. The only downward force is supposed to be gravity.

Measure the distance from where you will drop the ball to the floor

Mark a starting line on the floor. You will have to be walking as you cross this line so give yourself some room.

The meter stick will probably be long enough to show how far you walk dropping and catching the ball. Set is up from your starting line along the path you will follow.

Put the meter stick down with one end touching the starting line

Holding the ball, start walking toward the starting line

As you cross the starting line, drop the ball and start the stopwatch

Stop, stop the stopwatch when you catch the ball on the first bounce

Find the distance you went by looking at the meter stick

[You may want to have your friend work the stopwatch.]

Doing this can be difficult so you may want to repeat it a few times

Observations:

Describe the path the ball follows when you drop it:

Describe the path the ball follows when you drop it while walking:

Distance the ball is dropped:

For each trial with the ball write down the time and distance:

Analysis:

The falling projectile ball has two different movements so there are two different vectors.

When you drop a ball while walking, ti follows a curved path. In vectors this is shown with two vectors, one going forward for the momentum and one going down for the gravity. Added up the two show where the ball will land.

Vector 1 – Distance

One of the vectors points forward because you are moving forward. How far forward will the ball go?

We’ve seen this already. The distance is the time multiplied by the speed. You want to know about the part when the ball is going to the floor. As we saw in the last Project, this is half of the total. Divide the distance and the time in half.

Now you can rearrange the formula to v = d/t. Put in your values for d and t to find the velocity for the first vector.

Vector 2 – Falling

We’ve seen this already. Gravity is acceleration so the distance down equals gravity’s acceleration multiplied by the square of the time.

Remember the acceleration is 9.8 m/s2 and the time is what you used before. Put your values in and calculate the distance the ball dropped.

Now compare the distance you dropped the ball to what you calculated.

Looking at What Makes Your Values Change

We used several measurements in our calculations. One was the value for gravity. We used an accepted and proven value of 9.8 m/s2 so this will not change.

There are three measurements you need for a projectile. One is time. One is the distance to the ground. The third is the distance from dropping to catching the ball.

Now we have several measurements we made. One was the distance you walked between dropping and catching the ball. We assumed we dropped and caught the ball at the same height.

How accurately did you measure the distance? It must be in meters. If you measured the distance and the time in different tests, can you be sure the distance was the same both times?

Another distance was how far you dropped the ball. When should we have measured this distance? Why? Is there a way to make sure you drop the ball from the same height each time?

We also measured the time it took to bounce the ball. My ball bounced up very fast making it hard to time this accurately. What about your time?

In the last Project we threw a ball upwards. The force we threw it with was countered by gravity until the two were equal and gravity took over causing the ball to fall down. Half the time was spent going up and half coming down.

When we drop a ball, gravity pulls it down. When the ball bounces, the force of the ball hitting the ground makes it come back up. Different kinds of balls will bounce differently.

What kind of ball did you use? I used one of those rubber balls that bounces back as high as the height I dropped it from for the first bounce. This kind of ball would come very close to taking the same amount of time coming up as it did going down.

If you used a different kind of ball, this may not be true. That would mean your time value would not be right. That would make your calculations off too.

Taking Another Look At How This Works

A projectile differs from a falling object because it moves from a starting to an ending place. The projectile or ball we looked at went out horizontally and fell as it traveled across this distance.

The arc of the falling projectile has two vector parts. One is falling because of gravity. The other is going forward due to some force pushing it forward.

With the balls we dropped, what was the forward push? When we walk forward, we have something called momentum. We will look at this more closely in a future Project. This momentum provided the force forward to our balls.

Calculating the time it takes for the ball to fall to the ground uses the formula d = at2 where a is 9.8 m/s2 for gravity and d is the distance we measure.

Calculating how far forward the ball will go uses the formula d = vt. If we know how far the ball will fall, we can calculate time as above or we can measure it.

We must know the distance to calculate velocity or velocity to calculate distance. We must know two values for the formula to calculate the third.

Giving It another Try

This time let’s try to keep our measurements much more accurate. The first one is how far we will drop the ball.

The farther the ball drops, the longer it will take making timing easier. However, we need to have some mark so we drop it and catch it at the same height. The waist is convenient but may make timing difficult.

Measure the height to your waist.

Next is the distance you walk while bouncing the ball.You need to be walking along before you drop the ball. Have a route and a marked starting line. It may help to have a line or something marked to keep walking in a straight line. Have a way to mark the ending spot.

The hardest measurement is the time. The ball will bounce back up quickly. Having a friend time the bounce may be easier than trying to walk a straight line, drop the ball while starting the stopwatch and catching the ball as you stop the stopwatch.

You can do several trials but keep each set of measurements separate as each trial may differ in  measurements from the others. They should be similar so you can pick a set that seems more accurate to use for your calculations.

What Can You Calculate?

You can use your distance and time measurements to calculate your walking velocity using v = d/t.

You can use d = at2 where a = 9.8 m/s2 to calculate the distance the ball falls to the ground or the time it takes to reach the ground. Because the time is squared, you will want to use a calculator to find the square root or the time that was squared.

What We Will Do Next

Next week the Project will be a projectile challenge. We will calculate the velocity of a ball traveling off a table and use it to calculate where to place a cup to catch the ball when it reaches the ground. You will need two long ramps, a ball, a meter stick and a stopwatch. Oh, you will need a cup to catch the ball in.

# Physics 15 Projectile Motion

There’s straight line motion. Our balls and cars have shown us a little about it.

There’s circular motion. We used a nut on a string to find out a little about it.

One last type of motion is projectile motion.

What happens if you throw a ball straight up?

If you don’t dodge, it will come straight down and hit you. Why?

If you throw a ball across a room, it curves down to the floor. Why?

Question: How does projectile motion work?

Materials:

Ball

Stopwatch

Paper

Pencil

Procedure:

Toss the ball up from your hand

The ball leaves the hand, goes up then comes back down into the hand.

Observe how the ball goes up and down

Catch it when it returns to your hand

If you have a friend to help, have your friend gently toss the ball across a space

Observe how the ball moves

Throwing a ball or other projectile gives it an arch shaped path.

Play catch outside with your friend

Observe how the motion of the ball changes as you throw it harder

Start the stopwatch and throw your ball straight up as hard as you can [It helps to have a friend help with this.]

Stop the stopwatch when the ball hits the ground

Repeat this only if you did not get the stopwatch stopped on time

Observations:

Draw your ball going up and down one time

Describe how your ball goes up and down

Draw your ball going across a space

Describe the motion of your ball

Describe how the motion of your ball changes as the throws get harder

Time for your ball to go up and down:

Conclusions:

What makes your ball go up?

Newton’s First Law of Motion says an object in motion will continue that motion unless acted on by another force. What force keeps your ball from going up forever?

Why do you think the projectile motion of your ball changes as you change how you throw it?

Throwing a ball is more like the projectile motion people think of because the ball goes over a distance. At the beginning most of the force pushes the ball up, some goes sideways and gravity pulls down. At the top of the arch there is no more force pushing the ball up but it still has force pushing it sideways and gravity pulls it down. When the ball lands, only gravity is still pulling on the ball.

Draw your ball going across a space. Show your ball at the beginning, middle and end of the toss.

Add vectors to show how the forces are acting on your ball at each point to change how it moves.

How does projectile motion work?

Why can’t you use an average time for throwing your ball straight up?

Analysis:

How high did you throw your ball?

Your ball spent half its time going up and half its time coming down. Divide your time in half.

What provided the force to make the ball go up?

When the ball first leaves the hand, most of the force is pushing the ball upward with gravity pulling against it. At the top of the loop, gravity and upward force cancel each other out and the ball stops. Then gravity pulls harder than the upward force so the ball falls back down into your hand. This is projectile motion.

What provided the force to make the ball come down?

Remember the formula from the last Project was a = d/t2

This time we know the acceleration is 9.8 m/s2 and the time and want to know the distance. We can rearrange the formula to be d = at2

Calculate how high you threw the ball.

What I Found Out

First I found out this Project is much easier with two people and I am only one so pictures were not possible. So I did drawings on my computer.

Tossing a ball up and down in one hand isn’t hard. The ball went up out of my hand then stopped and fell back down into my hand.

Playing catch can be fun. When the ball is tossed easily, it arches up then down into the other person’s hands. As the ball is tossed harder, the arch flattens out until it is almost a straight line.

Throwing or tossing a ball uses force from my hand. Gravity is always pulling down on the ball.

Throwing a ball harder means it is going faster so gravity doesn’t slow it down as fast flattening the curve the ball makes.

The ball must go fast enough to overcome gravity. The harder I throw the ball, the faster it goes and the longer before gravity slows it down enough to make it fall.

In projectile motion the ball starts off with lots of force pushing it upwards. Gravity pulls a little of that force at a time slowing the ball down. At the top of the arch gravity is equal to the force making the ball go forward. Then gravity is greater making the ball fall down.

When a ball goes straight up, gravity pulls down until the ball stops and starts to fall down. Even if I try very hard, I won’t throw the ball with the same force every time so I must time each throw separately.

When I tossed my ball up, it took 1.94 sec to hit the ground. Half the time is .97 sec. Squaring the time gives .88 s2. Multiplying that by 9.8 m/s2 tells me I threw the ball 8.6 m or about 28 feet up.

# Physics 14 Gravitational Acceleration

As we’ve seen and used, gravity pulls things down to the ground. It causes what physicists call uniform acceleration. This means the object accelerates the same amount each second or unit of time.

Another way of saying this is that the object going speed in meters/second [m/s] per second moving [1/s] or acceleration [a] is m/s2.

In another Project we found gravitational acceleration is the same for large or small masses. Air can slow the object down due to friction. Remember the paper airplanes and the fan?

In this Project we will try to measure gravitational acceleration in two ways. This will require doing some math. Both ways require the stopwatch start when the ball is released so the ball starts from rest or velocity equal to zero.

Question: What is the value of gravitational acceleration?

Materials:

Ramp

Ball

Meter stick

Stopwatch

Procedure:

This is the hardest way. You drop the ball while timing how long it falls. The farther it falls, the easier it is to start and stop the stopwatch as the ball hits the ground. You must know exactly how far in meters the ball falls.

The ball must be held at the tape mark each time before it is dropped.

Mark the height you will drop the ball from.

Measure the distance from the floor to the mark in meters

Stand with the ball in one hand and the stopwatch in the other hand or have a friend help

Start the stopwatch at the same time you drop the ball

Stop the stopwatch when the ball hits the floor

Do this at least three times

The ramp was taped to the chair.

If you remember other Projects, running the ball down the ramp makes it take longer to get to the ground. This makes timing the ball easier. You must know exactly how far the ball rolls down the ramp to the ground.

I used a ramp two meters long propped and taped to a chair.

Mark your starting line on the ramp

Measure the distance from your mark to the floor in meters

Hold the ball in one hand at the starting line and the stopwatch in your other hand or have a friend help

Let the ball go at the same time you start the stopwatch

Stop the stopwatch when the ball reaches the floor

Do this at least three times

Observations:

Time for the ball to fall:

1st:

2nd:

3rd:

Time for the ball to go down the ramp

1st:

2nd:

3rd:

Analysis:

Find the average time for the ball to fall

Find the average time for the ball to go down the ramp

[Remember you add up all the times then divide by the number of times to find the average.]

To calculate the gravitational acceleration we will use the formula: a = v/t = d/t/t

The a is acceleration.

The v is the velocity of the ball when it hits the floor. You don’t know the velocity but velocity is distance divided by time and you do know these.

The d is the distance the ball travels in meters.

The t is the time in seconds.

Calculate the acceleration by dividing the distance in meters by the time in seconds then the quotient by the time in seconds again to get the acceleration for one second.

The ramp was steep so the ball sped down it quickly making timing difficult.

Use the same formula and the distance down the ramp and time for the ramp to calculate the acceleration down the ramp.

Conclusions:

Why is measuring the distance so important?

Why is measuring the time accurately so important?

Why do you use an average time?

Would it be better to have more times to use to get your average time? Why do you think so?

Why should the acceleration you calculate for the two methods of timing be about the same?

Were your two times the same? Why do you think this was the case?

The gravitational acceleration is thought to be 9.8 m/s2. Were your calculated accelerations close to this? Why do you think this was the case?

What I Found Out

This project seems so easy to do. I measured my ramp carefully so it was 2 m long. It was set up with a steep slope.

When I tried to time the ball going down the ramp, I had problems. It was easy to start the ball and the stopwatch at the same time. It wasn’t so easy to stop the stopwatch when the ball got to the floor.

Dropping the ball was even harder. Again it was easy to start the ball and the stopwatch at the same time. I’m positive the ball bounced before I got the stopwatch stopped.

This is definitely a project requiring two people to do it well.

The formula required two measurements. One was the distance the ball went. Since this distance is divided by the square of the time, a little mistake in measuring the distance can make a big difference in the answer.

The time is squared or multiplied by itself. Any mistake in the time becomes very big.

I measured the time four times each way the ball went. The times were very similar for going down the ramp with a span of only .03 sec between the lowest and highest times.

The times for dropping the ball had a range of .1 sec between the lowest and highest time. The range of the squares would be .19 sec2 to .29 sec2. That much difference would make a big change in the acceleration I calculated.

My ball dropped 1.5 m faster than I could start and stop the stopwatch. This made getting good times difficult.

Using an average time smoothed out these extremes to give me a better time for my calculations.

The procedure said to use three time measurements. I chose to use four because my measurements were so different. If the three measurements had been more similar, I would have used only three.

I think the number of measurements you use depends on how similar they are.

When I calculated my accelerations I got 1.5 m/s2 for dropping the ball and 1.3 m/s2 for the ramp. Since the pull of gravity was the same for both methods, the acceleration should be about the same.

My calculated acceleration was very different from the accepted gravitational acceleration of 9.8 m/s2, not even close. I am not sure why my values were so different.

One possibility is the time. It was very hard for me to get a good time even though my values were similar.

What I would like to do is repeat this project with someone to help me. I would make two other changes.

First I would lower the angle of the ramp so the ball would go down a little slower making timing it easier.

Second I would lengthen the distance to at least two meters dropping the ball. This would give a little more time to stop the stopwatch before the ball bounced.

# Physics 13 Acceleration and Speed

All forms of motion involve either speed or acceleration. What is the difference?

Speed in physics is how far something moves in a given time.

Acceleration in physics is a change in speed or direction or both.

Straight line motion is an easy way to look at both acceleration and speed.

This Project is easier with two people.

Question: What is the difference between speed and acceleration?

Materials:

Stopwatch

Meter stick

Ball

Short ramp 1 to 1.5 m long

Long ramp 4 to 5 m long

Tape

Marker

Procedure:

Make the two ramps [Plastic car track will work, if you have it. Mark the long ramp with masking tape.]

I used stiff cardboard because it is smooth, easy to get and easy to work with. My piece was over a meter square. I cut long strips of cardboard about 15 cm wide.

My cardboard was thick and stiff making folding difficult. The fold does need to be fairly straight. Fold up one end so the ends are the same then start folding. Start the fold at the other end the same way then move each fold up toward the middle of the piece.

One piece was folded in half lengthwise for the short ramp.

Each piece for the long ramp overlapped the other by 10 to 15 cm to add strength to the joint. Each overlap had to have the same top and bottom overlap so the ball would always run from the top piece to the bottom piece to minimize friction.

Several pieces were taped together to form the long ramp. First fold each piece in half lengthwise. Each piece must overlap 10 cm or so. The top piece always overlaps the next piece. The folds must be in the same place at each overlap. Tape each one top and bottom.

Because the long ramp would tend to sag down, I put extra duct tape over the joint to strengthen it.

Mark across the long ramp 20 cm from the end. Make a second mark 1 m from the first mark.

In putting the duct tape on the inside of the ramp, I put it in the fold first then smoothed it upwards.

Make another mark 20 cm from the second mark. The next mark is 1 m from the third mark.

I numbered each marked meter on the long ramp with the top one being one. Each meter did span one of the taped areas but duct tape is smooth and few if any wrinkles were in the area the ball ran down minimizing friction and allowing the ball to run freely down the ramp.

Go down another 20 cm and make another set of marks 1 m apart.

Set up the short ramp so the top is 50 cm off the floor. The floor must be smooth, not carpeted.

Masking tape holds the ramp in place. Tape keeps the ramp straight so the ball will go straight. The meter stick was moved after this as the ball hit it instead of going by.

Set the meter stick on the floor 10 cm from the end of the ramp so the ball will go past it

Let the ball go down the ramp and time how long it takes the ball to go the 1 m  past the meter stick

Do this three times

Move the meter stick so the end is 1 m from the end of the ramp

Time how long it takes the ball to go past the meter stick at least three times

Move the meter stick so the end is 2 m from the end of the ramp

Time how fast the ball goes past the meter stick at least three times

Set the long ramp up so the top end is 50 cm off the floor [If the ramp sags anywhere along its length, prop it up.]

The long ramp was not quite straight. Only one prop was under it so the bottom sagged too much. It tried to tip over and required additional taping to the floor.

Time how fast the ball goes the first meter at least three times

Time how fast the ball goes the second meter at least three times

Time how fast the ball goes the third meter at least three times

Place the meter stick on the floor 10 cm from the end of the ramp

Time how fast the ball goes this meter at least three times

Observations:

Short ramp-

1st meter:

2nd meter:

3rd meter:

Long ramp-

1st meter:

2nd meter:

3rd meter:

Floor meter:

Analysis:

Calculate the average time for each set of times for the short and the long ramps.

Draw a graph of time and which meter was run for the short ramp

Draw a line through the times

Add the times for the long ramp to the graph

Draw a line through the times

The times from the short ramp for the different meter placements were very similar. They did gradually increase but all stayed between .3 sec and .38 sec giving a fairly straight line on the graph. This indicates we were measuring speed. The times from the long ramp changed a lot for the different meter sections giving a steeply curved line on the graph indication we were measuring acceleration.

Conclusions:

Does the speed of the ball seem to change for the short ramp? Why do you think so?

The ball sped down the short ramp and past the meter stick almost faster than I could start and stop the stopwatch.

Does the speed of the ball seem to change for the long ramp? Why do you think so?

Are you measuring speed or acceleration for the ball and short ramp? Why do you think so?

Are you measuring speed or acceleration for the ball and long ramp? Why do you think so?

If you could time the ball for the top and bottom halves of the short ramp, would the times be the same? Why do you think so? Is the ball accelerating on the short ramp?

Does the length of the ramp matter to the final speed of the ball? Why do you think so?

What could cause the ball to slow slightly from the short ramp?

What I Found Out:

I missed having Aiah to help with this Project. Two people working on it makes this much easier.

The short ramp was quick and easy to make and set up. My ball passed the first meter in .34 sec, .38 sec and .28 sec for an average of .33 sec. The ball ran the second meter in .41 sec, .25 sec, .31 sec and .28 sec. for an average of .31 sec. This was the hardest meter for me to time. The times for the third meter were .40 sec, .31 sec and .37 sec for an average of .36 sec.

The three average times for the short ramp were very similar. The speed does not seem to change for the distances from the ramp. This would be a measure of speed as the ball travels at about the same rate in the same direction.

The long ramp was harder to assemble. Duct tape holds it but I had to use a lot of it to keep the pieces from pulling apart. The prop under the ramp keeping it from sagging helped hold it together too.

The ball ran much slower down the long ramp making it easier to take a picture but the ball went faster for each meter and was going at the same speed when it got to the bottom as it had from the short ramp.

The first meter was the hardest to time for the long ramp. My times were .97 sec, .94 sec and .90 sec for an average of .94 sec. The times for the second meter were .59 sec, .56 sec and .50 sec for an average of .55 sec. The third meter times were .47 sec, .40 sec and .46 sec with an average of .44 sec. When I timed the meter on the floor, the times were .31 sec, .41 sec, .44 sec, .34 sec and .41 sec with an average of .38 sec.

While the ball is going down the long ramp, it goes faster each lower meter. The time it takes for the meters gets shorter so it must be going faster. This would be a measure of acceleration because the ball’s speed is increasing or changing.

If I could time the ball going down the short ramp, the ball would go faster on the bottom half of the ramp than on the top half. I think this because the ball has no speed when I first let it go and it is going very fast when it gets to the bottom. The ball’s speed is changing as it goes down the ramp so it is accelerating.

When I compare the average speeds of the ball for the first meter covered on the floor for the two ramps, they are similar. Even though the ball went much farther to get down the long ramp than on the short ramp, it accelerated the same amount. The length of the ramp does not matter.

What does matter is friction. This gradually slows the ball down as it rolls across the floor.

# Physics 12 Harmonic Motion

In physics motion happens when something changes its position. We’ve watched toy cars and balls race down ramps for straight line motion. Nuts swung back and forth for pendulum motion. A nut went in a circle for circular motion. How else can something move?

Pick up a ball point pen and press the end. The knob pushes in then out again. It moved but why does it move that way?

If you take the pen apart, you find a tiny spring inside. You can compress or push the spring down then release it and it goes back to its original length.

Springs are very useful items. They show harmonic motion. They can be used to build a spring scale.

Question: What is harmonic motion?

Materials:

Spring as from inside a pen

A length of wire

Procedure:

Hold most of the Slinky in your hand allowing part of it to dangle down

Move your hand up and down then keep it still

Hold the small spring between your thumb and finger

A spring does show harmonic motion but only when force is directly applied to the coils to compress or pull apart the coils then easing off to allow the coils to return to their original position.

Press the spring down then let it loosen several times [Don’t let go of it, keep it between your thumb and finger.]

Pull the spring out a little longer and let it go back several times

Wrap the wire around something round like a marker or a pencil keeping the coils close together

The wire coils must be tight around the pencil and close together to create a spring.

Attempt to compress and release these coils

Attempt to pull and release these coils

Observations:

The coils of the Slinky go down and up in harmonic motion. All springs show some amount of this motion but this toy shows it very well.

Describe compressing and releasing the spring [amount of force needed etc.]

Describe stretching and releasing the spring

Describe how your coiled wire behaves

Conclusions:

Is speed constant in harmonic motion? Why do you think this?

Does the spring seek to maintain a certain length and shape? Why do you think so?

What do you think would happen if you compressed the spring then let it go?

Compressing an unsupported spring shows a problem engineers face building columns, the spring buckles to the side. If the compression continues, the spring sill shoot off to the side.

What do you think would happen if you pulled the spring out to twice its length?

How does a spring keep its ability to produce harmonic motion?

Does a tightly coiled wire behave differently from a straight wire?

Does the shape of a spring affect how it behaves?

What I Found Out:

The end of my Slinky went down then up over and over. Eventually it stopped but it took a long time.

When I looked at the pictures of the Slinky in motion, I could see the coils stretching out from top to bottom. They didn’t stretch out very far. Then the coils pulled back together as the Slinky pulled back up.

Watching the end of the Slinky, the wire loops zoomed down then stopped, zoomed back up and stopped. The speed was not constant as the loops slowed to a stop, sped up then stopped to start over again.

Once the Slinky stopped moving, gravity pulled the coils out a little. Otherwise the Slinky tried to keep its coils close together.

The small spring compressed down until the coils touched each other and returned to its original length. Pulling the spring stretched out the coils. When the spring was released it returned to its original length.

If I pulled the spring until it was twice its length, the coils straightened a little. The spring returned a little but not to its original length.

Coiling a wire seems to make the wire try to behave like a spring.

A spring seems to need to keep its coils in a certain position. The harmonic motion is produced when the coils are pushed or pulled out of position.

A straight wire stayed bent when I pushed it over. It didn’t straighten out again until I straightened it out.

My wire was hard to wrap around a fat pencil. When I pushed the coils together, it got harder as the coils got closer together. After releasing the coils, they moved out a little way then stopped. These coils acted a little like a spring. They would compress and return to place, pull a little and return to place.

The wire I used had been heated and cooled. From a Chemistry Project, wire that is heated and cooled behaves differently from wire that hasn’t been heated and cooled. It is stiffer and more brittle.

That makes me think, if I had new wire and wrapped it around a pencil, it would act more like a spring.

# Physics 11 Circular Motion

Things move in different paths. So far we’ve looked at straight motion and pendulum motion. What if a pendulum didn’t swing back and forth but went all the way around? This is circular motion. How is circular motion different from pendulum motion?

Question: How does circular motion work?

Materials:

String

Nut

Procedure:

Cut a piece of string 1.5 m long

Measure off 1.5 m of string. My string unravels easily so I put a piece of tape over the end to hold it together.

Put a loop in one end big enough to fit on your wrist

The loop at the end of the string needs to be big enough to slide over a hand but small enough to not slip off the wrist easily.

Tie the nut to the other end of the string [I taped the knot as my string doesn’t hold a knot well.]

The nut is tied to the end of the string. Be sure to secure the knot so it will not come loose while you are swinging the nut around. I used tape.

Measure up the string 0.5 m and make a small knot

The first knot is tied 0.5 meter from the nut.

Measure up the string 1 m and make a small knot

The second knot is tied at 1 meter from the nut.

!Warning!: Getting hit by the nut can hurt. Hitting something else with the nut can get you into a lot of trouble picking up broken things off the floor.

Put the loop around your wrist

Hold the string at the first knot

Swing the nut back and forth like a pendulum but keep adding force until the nut goes all the way around

Swing the nut around in a circular path several times

Stop the string

Hold the string at the second knot

Swing the nut back and forth like a pendulum but keep adding force until the nut goes all the way around

Swing the nut around in a circular path several times

Stop the string

Observations:

How did you have to move your hand to add force to increase the swing of the nut?

The nut swings at the end of the string. The hand holding the string keeps the nut moving at a fixed distance so it travels in a circular path.

Describe any differences for the longer string

Describe how it felt as the nut moved in a circular path

Describe any differences for the longer string

Conclusions:

Why do you loop the string around your wrist?

If you put a little bit of force into making the string swing, does the nut go all the way around?

Does the nut want to continue in a circular path or does it try to leave that path? Why do you think so?

What will the nut do if you let go of the string? If you decide to test this, be sure you are outside and not swinging the nut toward anything like a window. Take the loop off your wrist, swing the nut so it is going in a circle and let go of the string as it tops the circle. You can get a little idea of what it does by leaving the loop around your wrist, swing the nut by the first know and letting it go at the top of the circle. Be aware the nut could hit you when you do it this way.

Compare the speed of using a short string and using a long string. If you decide to time the swings, have a friend use the stopwatch. It would be easier to get an accurate time if your friend times three to five revolutions instead of one.

Try drawing the vectors to show how the nut travels in a circular motion. Remember one vector will follow the string as it holds the nut in the pathway. Which way will the nut’s forward vector point? Will it be curved or straight? Does gravity have much of an effect on this motion?

What I Found Out:

The nut was easy to put on the string. If it hits something breakable like a window, this is bad news. Keeping the string attached to my wrist and taping the knot holding the nut on the string made sure it couldn’t fly off and hit anything or anyone.

My hand swung back and forth to make the nut swing. This hand movement could turn the nut into a pendulum, even one that went very high. It did not make the nut go around in a circular pathway.

I had to move my hand in a circular path to get the nut to go around. With the short string, the nut went around very easily. It was very hard to slow down enough for the nut to not go around.

The longer string took more and bigger movements of my hand to get it started going around. If I slowed down at all, the nut would make only a partial circle and fall down toward the ground.

Once the nut was going around on the long string, I could make the same small movements with my hand to keep it going as long as I kept it going fast enough to go around.

I think gravity pulls on the nut. When the nut is going fast enough, gravity can’t pull hard enough to make it fall. If the nut slow down, gravity takes over and pulls it down.

I could feel the nut pulling on my hand as it went around. There was a bigger pull with the longer string.

When I let go of the string, the nut flew out away from the circular path. I had to keep the loop around my wrist doing this so the nut hit the end of the string and fell to the floor.

The nut was traveling fairly fast around the path making timing challenging. The short string gave me 3.09 sec and 3.06 sec for five times around. The long string times to 3.62 sec and 3.56 sec. The longer string seemed to give a longer time for each revolution. I would wonder how accurate this is because I could not measure the force used to make the nut go around so this may have been very different for the long and short strings.

There are three vectors interacting in circular motion. One points in to the center of the circle holding the object in its circular pathway. One is the pull of gravity. One is the straight line motion path the nut would take if the other two forces did not exist.

Drawing the vectors depends a little on where the nut is on the circular pathway. One vector arrow must point down toward my hand. I know this because I had to hold onto the string and felt the nut trying to pull free.

One vector arrow will point down toward the ground. This is gravity. It is a smaller arrow as the nut is going around, not falling straight to the ground.

The last vector arrow goes straight out from wherever the nut is. The nut is trying to go in a straight path. The vector arrow pointing to the hand keeps it from flying off so the straight vector is bigger than the gravity arrow and smaller than the one going to the hand.

# Physics 10 Pendulum Motion

Both Galileo and Isaac Newton came up with the laws of motion. Yet we call them Newton’s Laws of Motion. Why?

Time.

Newton could measure time and Galileo could not. Why didn’t Galileo go out and buy a watch? Because there were no watches or clocks in the early 1500’s.

One way Galileo tried to measure time was with his pulse. A pulse is how fast a heart beats. Can you take your pulse?

There are two ways you can take your own pulse. One is in your neck Press your first two fingers against your neck on the side near the top of your trachea or windpipe.

Be sure to use your fingers not your thumb to take your pulse. Your thumb has an artery in it and you will feel this too making your pulse count confused.

The second place is in your wrist. Feel on the inside of your wrist below your hand. There is a hard ridge of bone then a softer area. Several tendons like hard ropes run up your wrist. Press your fingers in beside these below your thumb. You can feel your pulse beat.

Both of these take a little practice. I find it easiest to find the one in my neck. It’s easier to find the wrist pulse in someone else’s wrist.

Galileo would use his pulse to time balls running down a ramp. Stop and think about the last Project. Would Galileo use a steep ramp or one much flatter?

Once you can take your own pulse, watch a clock with a second hand and count the beats for 15 seconds. Get up and run in place or jump up and down 15 times. Now count your pulse again.

Is using your pulse to time some event very accurate?

Galileo decided to try to make a more accurate clock. He used a kind of motion to build a pendulum clock.

For this Project, the pole must be level, the eyes hanging down and far enough from a wall so the nuts will not hit it.

Question: How does a pendulum work?

Materials:

String

Meter long board with small metal eyes or staples in it

A screw eye looks like a screw with a metal loop for a head.

Heavy and light metal nuts, one of each

Stop watch

Ruler

Procedure:

Put two small eyes or staples 20 cm apart near the center of the board

Be sure the eyes or staples have their holes parallel to the board

The two eyes need to be far enough apart for the two pendulums to swing without tangling.

Secure the board between two chairs or tables so the board is level

Cut two lengths of string 60 cm long

Tie a heavy nut to one string and a light one to the other string

Put one string through the eye or staple and tape it to the stick so 15 cm of string hangs from the eye to the nut.

The pendulum string between the knot over the nut and the bottom of the eye is 15 cm. The extra string goes up through the eye, wraps around the pole and is taped in place.

Do the same on another eye with the other string

Pull the nuts up to one side even with the eyes

Released together the heavy and light pendulum nuts swing at the same time to begin with. The string shifted the direction of the swing and changed the timing.

Let the nuts go and watch how they move

Do they move together or is one faster than the other?

Pull one nut to the side level with the eye with the string tight

Pull the nut up level with the eye with the string tight before letting it go.

Start the stopwatch as you drop the nut

Count five times the nut comes back to where it started and stop the stopwatch

Do the same with the other nut

Lengthen the strings to 30 cm and repeat what you just did

Lengthen the strings to 45 cm and repeat these steps

Observations:

Compare how the two nuts swing

Times for five swings:

Five swings of the 15 cm pendulum does not take very long. it is hard to judge when the pendulum reaches the top of a swing.

Light nut, 15 cm:

Heavy nut, 15 cm

Light nut, 30 cm

Heavy nut, 30 cm

Light nut 45 cm

Heavy nut, 45 cm

Analysis:

Calculate the average time for one swing for each trial run

Light nut, 15 cm:

Heavy nut, 15 cm

Light nut, 30 cm

Heavy nut, 30 cm

Light nut 45 cm

Heavy nut, 45 cm

Conclusions:

How accurate do you think your times were? Why do you think so?

Is mass or string length what determines the time of a swing?

The two 30 cm long pendulums are set up.

Can you tie a string so the nut takes five seconds to complete one swing?

Do you think a pendulum will swing forever without being restarted? Why do you think so?

How could Galileo use this type of motion to make a clock?

What do you think would happen if you shook the board while one of the nuts was swinging? Try it and find out.

Would a pendulum clock always be accurate? Why do you think so?

What I Found Out:

I found it difficult to make the strings exactly the same length for the two different nuts. Another problem was when I released the nuts to swing like pendulums. For the first five or six swings they went back and forth then started shifting until they were swinging up and down the pole until they were swinging the opposite way across the pole. This was better when I tied the string off with a loose knot at the eye. It might improve how the nut swung if the string had been tied off each time instead of going through the eye.

The next difficulty was holding the nut up to exactly the same height each time. Putting another board or something else stiff across to bring the nut up to each time would make sure the height was the same each time.

Starting the stopwatch at the same time I released the nut was not as hard but I was probably not as accurate as it seemed I was.

The end result was that my times were probably not as accurate as I wanted them to be. In fact, it is surprising how similar each set of times were.

When I released the heavy and light nuts together, they swung at about the same time. This was the case until the strings shifted. That made me think the mass at the end of the pendulum was not the deciding factor in how fast the pendulum moved.

For my light nut the 15 cm string had an average time of 4.63 sec, the 30 cm string was 6.17 sec and the 45 cm string was 7.65 sec. For the heavy nut the 15 cm string had an average time of 4.75 sec, the 30 cm string was 6.44 sec and the 45 cm string was 7.81 sec.

The longest pendulums take the longest to make five swings. The time of a swing depends on the length not the mass.

Comparing the 15 cm strings gave me 4.63 sec and 4.75 sec. The 30 cm string gave me 6.17 sec and 6.44 sec. The 45 cm string gave me 7.65 sec and 7.81 sec.

This confirmed that the mass of the nuts did not determine the time of a swing. Instead, the longer the string was, the more time a swing took.

Since 5 sec is about half way between the times for the 15 cm and 30 cm strings, I would try a string 22 cm long for a 5 sec swing. I did not have time to test this idea.

I did notice that each swing was a little smaller than the previous swing. Part of this would be the shift in how the string was swinging. Part of this would be friction between the string and eye. Even tying the string to the eye did not stop the pendulum from slowing down. That means a pendulum would not continue swinging forever.

Since a pendulum can swing in the same time if friction is minimized or countered, Galileo could make a pendulum clock. Each swing of the pendulum would have to move a second hand which would move a minute hand which would move an hour hand.

In fact, Galileo did make such a clock. Clocks are still made with pendulums. They use weights to counter the friction and keep the pendulums swinging at the same speed. The pendulums turn gears that move the clock hands to show the time.

Shaking the pole would change how the nuts were swinging. Moving the chair made the swings change size and direction.

A pendulum clock would have to sit still to work properly. If the ground moved or it was on a ship, the pendulum swings would not stay the same so the clock would not be accurate.

# Physics 9 Acceleration

Speed is the distance something goes in a certain amount of time. The speed stays the same. Except we know things go faster or slower and change direction. This is acceleration.
When Albert Einstein developed his Theory of Relativity, he made an assumption about gravity. He said it was a form of acceleration.
If gravity is a form of acceleration, it will make an object’s speed change over time.
Galileo worked with gravity too. He rolled balls down a ramp and found out something interesting about their final speeds.

I used the same set up I used for measuring speed. the ball ramp was taped to the chair with the meter stick on the floor.

Question: How does gravity change a ball’s speed?
Materials:
Ball ramp
Ball
Meter stick
Stop watch
Procedure:
Mark a place on the ramp to start rolling the ball
Measure the distance the ball will roll and divide it by four
Measure one fourth the distance and put a mark

Each place on the ramp must be clearly marked. Will the ball go twice as fast from the top mark as from the half way mark?

Measure one half the distance and put a mark
Measure three fourths the distance and put a mark
Set up your ramp with the top mark0.5 m high
Set up the meter stick on the floor beside where the ball will roll with the beginning 10 cm from the end of the ramp
Write down how you think the ball’s speeds will compare for the four different starting points [Will the ball go half as fast when started half way down the ramp?]
Do at least three trials starting the ball from each mark.
You will start the stop watch when the ball reaches the beginning of the meter stick and stop it when the ball is at the end of the meter stick.
Observations:
Write down the four distances on the ramp:
Highest 1:
2:
3:
4:
How will the speed of the ball compare for each starting point?
Times for 1:
1:
2:
3:
Average
Times for 2:
1:
2:
3:
Average:
Times for 3:
1:
2:
3:
Average
Times for 4:
1:
2:
3:
Average

Aiya Taylor helped me with this project by letting go of the balls on the ramp. Help is important for these projects.

Analysis:
Calculate the average time for each starting point by adding up the times for the trials and dividing by the number of trials.
Draw a graph of speed and height. (Use 1/4, 1/2, 3/4 and 1 for the height.)
Conclusions:
Are you measuring final speed or acceleration? Why do you think so?
Is this measurement a good way to judge acceleration? Why do you think so?
Speed is constant so the line on your graph would be straight. Is your line straight?
Galileo decided gravity added acceleration at meters per second (speed) per second. This gives a curved line on a graph. Is your line curved?
Does your graph show speed or acceleration?

What I Found Out:
My ball had an average time of 44 seconds for the top mark. The time decreased to 39 seconds for the 3/4 mark. The time increased to 47 seconds for the 1/2 mark. The 1/4 mark had a time of 93 seconds.
It was hard to get good times for each trial run. But the time was definitely increasing as the height decreased. I think the 3/4 mark average was not accurate.
Because the ball was running on the level floor when I measured the time, I was measuring final speed not acceleration. The final speed was produced by the acceleration on the ramp so it was a good way to compare how much acceleration the ball gained at each height.
My graph was not a straight line so it showed acceleration.

# Physics 8 Speed

So far we’ve seen vectors showing direction of a force and distance and direction of motion. Motion is a change in where an object is.

Sometimes that motion is very slow. Other times the change is very fast. The measurement of how fast something moves is speed.

Notice speed concerns two things. One is distance as the object is moving from one place to another over a distance. The other is time. It measures how much distance an object goes in a certain amount of time.

Measuring distance requires a meter stick. Measuring time requires a stop watch.

Although it is possible to do Projects using a stop watch by yourself, having help makes them much easier.

Scientists use the metric system. If you don’t have a meter stick, you can use a yardstick. You can convert yards into meters by multiplying the yards by 0.914 meters per yard. For measurements in inches you multiply by 2.540 centimeters per inch.

Remember our Project about forces and friction when getting ready for this Project. You need a smooth floor without carpet this time to minimize friction. If you can’t find a place like that, put down smooth cardboard so the ball rolls over it at least a meter.

Question: Does mass affect speed?

Materials:

2 balls of different weights

Ramp 1 meter long for the balls

Meter stick

Stop watch

Scale

Procedure:

Mass the balls and record the masses

My heavy ball is a rubber ball with a mass of 18.00 g.

Set up your ramp so the end is 0.5 m high where you will start the balls

I taped the ball ramp to a chair so it would remain the same for the entire project.

Put the meter stick on the floor 10 cm away from where the ball will roll onto the floor but not so the ball will hit it

Mark where you will start the balls

Putting a mark on the ramp means the ball is released at the same point each time so it’s final speed will be the same each time.

Write down your prediction of whether speed is affected by mass or whether the light ball or heavy ball will be faster or if they will be the same.

You will start the stop watch when the ball gets to the meter stick and stop it when the ball gets to the end of the meter stick

Time how fast each ball covers the meter. Do each ball at least three times. Record the times.

Observations:

Mass ball 1

Mass ball 2

My light ball is plastic with a mass of 3.07 g.

Times for ball 1

1:

2:

3:

Average t:

Times for ball 2

1:

2:

3:

Average t:

Analysis:

Average the times for each ball by adding up all the times then dividing by the number of trials.

Conclusions:

Compare the speeds of the heavy and light balls.

Do you think mass affects speed? Why do you think so?

Aiah Taylor, 5, helped with this project by releasing the balls down the ramp so I could time them.

What I Found Out:

The first thing I found out was that it is impossible to let a ball go down the ramp, back up to take a picture and time it for 1 meter at the same time. Luckily for me I found someone to help. Aiah Taylor was home from kindergarten for the day and was happy to let the ball go down the ramp whenever I asked.

My light ball had a mass of 3.00 g. the heavy ball had a mass of 18.00 g.

When we dropped the two balls, one heavy and one light, they fell at the same rate. I think their speed will be the same too.

The heavy ball had .44 sec for all three trials. That gave an average of .44 sec.

The light ball had .44 sec, .48 sec and .35 sec. That gave an average of .42 sec which was almost the same.

I found it was very difficult to time the ball for the 1 meter as it was going so fast.

Since the speeds were so similar, I don’t think mass affects speed.

# Physics 7 Motion and Vectors

For the Projects we’ve done so far we’ve accepted that the paper, the car, the balls and the jar moved. What is motion?

Look up motion in the dictionary. What does it say?

My dictionary says motion isthe act of changing place or moving.

We used vectors earlier to show the direction of a force. Vectors can also help us show where and how far something is moving.

Another concept in physics is displacement. This is how far something moves from its original position. This is not the same as the distance something moves.

Question: How can vectors show how something moves?

Materials:

Sheets of Grid paper [quarter inch is fine]

Pencil

Procedure:

Draw a line across a sheet of grid paper about ten squares from the top

The line is a street

Make a little mark across this line every second square

These marks show blocks

Draw a little house at the middle mark on the line

On a map east goes to the right, west to the left, north up and south down.

Trip 1:

You leave the little house and walk three blocks east to the market

Above the line you can make a fancy house and market. Below the line is room for the vectors. The first one goes from the house east to the market. It has an arrow on the tip pointing the direction you walked.

To show this draw a line from the mark in front of the house three blocks east or and put a little arrow at the end of the line.

Now you walk three blocks west back to the little house

You now walk back home so the vector arrow goes from the market to your house. The arrow is now on the end at your house as you walked that way.

Draw another line from the market to the little house and put a little arrow on the end

Conclusions:

How far did you walk?

This is distance. Your total distance is 3 blocks east plus 3 blocks west or 6 blocks.

Notice on your graph the arrows are equal and opposite. The vectors say you did not go anywhere.

Displacement is how far something moves away from where it started. In this case the displacement is 0 because you started and ended at the same place.

Trip 2:

Draw another line about ten squares below the first line and put a little mark in the middle

The long green line is the street running east and west with a mark showing your house in the middle. You can draw houses above the line if you wish.

This time each square is a block

You go to a friend’s house five blocks west of your house

The first vector is you going five blocks west so the line goes five squares to the left.

Draw this vector

The two of you decide to go to another friend’s house seven blocks east of where you are

Going seven blocks east means going past your house plus another two blocks and the vector shows this.

Draw this vector

Later you and your first friend go to your homes for dinner

You go only a short distance and your friend keeps going so two vectors are needed. I labeled them with a y for you and an f for friend so i would know which was which.

Draw these vectors

Conclusions:

Trip 2:

What distance did you walk?

What distance did your first friend walk?

What distance did your second friend walk?

What is your first friend’s total displacement?

Observations:

Mark your home in the center

Walk the five blocks west to your friend’s house

[Hint: This may be easier if you use more than one color for the vectors such as one to you alone, one for you and your first friend, one for the three of you and one for your two friends.]

The two of you walk seven blocks east to your other friend’s house

The three of you go five blocks east to a park for the afternoon

The three of you go to your house for supper

Your two friends go back to your first friend’s house for the night

Conclusions

What distance did you go?

What distance did your first friend go?

What was your first friend’s displacement?

What distance did your second friend go?

What was your second friend’s displacement?

What I found Out:

I used four different colors and labeled the vectors to keep track of them. Another way would be to do three graphs, one for each person. That method would make it easier to see how far and where each person went.

I walked 5 blocks W + 7 blocks E + 5 blocks E + 7 blocks W or 24 blocks. My displacement was 0 because I started and ended at home.

My first friend walked 7 blocks E + 5 blocks E + 7 blocks W + 5 blocks W or 24 blocks.  My first friend’s displacement is 0 because of starting and ending at home.

My second friend walked 5 blocks E + 7 blocks W + 5 blocks W or 17 blocks. My second friend’s displacement is 7 blocks because of starting at home and ending at my first friend’s house.

# Physics 6 Friction

Rub your hands together. Do your hands get warm? Why do they get warm?

Two surfaces like your two hands catch at each other when they are rubbed together. It’s called friction.

Question: How does friction affect gravity?

Materials:

Room with carpet

Ball ramp

Light and heavy balls

Wooden ramp

Meter stick

Jar with lid

Water

Procedure:

Prop up the ball ramp 0.5 m

Roll the light ball down the ramp several times

Note: If the ball rolls farther than the room wall, start the ball lower down on the ramp. Both balls must start at the same place on the ramp.

Roll the heavy ball down the ramp several times

Roll the light ball down the ramp and mark where it stops

Roll the heavy ball down the ramp and mark where it stops

The red ball is lighter than the rubber ball. The heavier ball rolls farther before it stops.

Measure how far apart the two places are

Prop up one end of the wooden ramp 0.5 m

Roll the empty jar down the ramp several times

Even started half way down the ramp the jar is rolling very fast when it gets to the floor.

Note: Start lower down on the ramp if the jar rolls too far across the floor and hits the wall. The empty, half full and full jars must start at the same point on the ramp.

Roll the empty jar down the ramp and mark where it stops

Fill the jar half full with water and put the lid on tightly

Predict whether the jar will roll farther, the same distance or a shorter distance

Roll the jar in your hands and see what the water does inside the jar

Gravity pulls the water to the bottom of the jar and keeps it there even when the jar is rolled in the hands or the jar rolls down the ramp.

Roll the jar down the ramp several times

Roll the half full jar down the ramp and mark where it stops

Fill the jar with water and put the lid on tightly

Predict whether the jar will roll farther, the same distance or a shorter distance

Roll the jar in your hands and see what the water does

Roll the jar down the ramp several times

Roll the full jar down the ramp and mark where it stops

Compare where the empty, half full and full jars stopped

Observations:

Which ball rolled the farthest

How much farther this ball rolled

Describe what the water does when you roll the half full jar in your hands

Describe what the water does in the full jar when you roll it in your hands

Predictions:

How far the full jar will roll

How far the half full jar will roll

How far will this jar roll before stopping? Does putting water in the jar change how far it will roll?

What happened:

Which jar rolled the farthest

Which jar was in the middle

Which jar rolled the shortest distance

Conclusions:

Draw a ball rolling on the carpet. Add the vector arrows to show the forces acting on it

In the last Project we found that gravity pulls the same on a light and a heavy ball. Does friction act the same on a light and a heavy ball? Why do you think so?

Does your carpet have a lot of friction? Why do you think so?

When your jar rolled in your hands, did the water roll with it? Why do you think so?

Draw the empty jar on the carpet and the vector arrows showing the forces acting on it

Does this drawing look a lot like the one of the ball?

Draw the half empty jar on the carpet and the vector arrows showing the forces acting on it

Is there another force arrow on this drawing? [Remember what the water is doing.]

If the half full and full jars were just that much heavier than the empty jar, do you think they would roll farther?

How does the water change how far the jars roll even though the water adds weight?

The ball on the left marks where the half full jar stopped. The next ball is where the full jar stopped. The ball on the right, much further than the others, marks where the empty jar stopped.

What I found Out

I set my ball ramp up and rolled the light ball down from the top. It raced across the carpet and hit the far wall. I had to release the ball about half way down the ramp for it to stop on the carpet.

The heavy ball raced across the carpet a little over a meter farther than the light ball. Since both balls ran over the same piece of carpet, the friction on the balls would be the same. However the heavy ball rolled a meter further so friction took longer to stop the heavy ball than the light ball. Friction is affected by weight.

The carpet is indoor outdoor carpet with short tight stiff loops packed close together. It doesn’t seem to have a lot of frictional force as the balls roll easily across it.

The first time I released the jar from the top of the ramp, it rolled across the carpet and hit the wall. I had to release it about half way down the ramp just as I did the balls. I marked where it stopped with a ball against the wall so the other jars would not hit my marker and move it.

When I rolled the half full jar in my hands, the jar turned easily. The water stayed level with the floor unless I turned the jar very fast so the water couldn’t run off the jar sides fast enough. The water moved opposite to the way the jar was moving.

Heavier things roll further than lighter ones so the half full jar will roll further than the empty one. At least that is what I thought would happen.

The half full jar stopped long before the empty jar had. The water was pushing to stop the jar from turning along with friction from the carpet.

When I rolled the full jar in my hands, there were a couple of bubbles in it so I could see the water was acting the same as in the half full jar.

After seeing that the water’s friction slowed the half full jar, I thought the full jar would not roll as far as the empty jar even though it had more weight.

When I released the full jar, it did roll farther than the half full jar. This must be because it weighed more. It did not roll as far as the empty jar so the water slowed it down.

If the three jars had just had different weights, the heaviest jar would roll the farthest and the lightest one the shortest distance like the light and heavy balls.

# Physics 5 Gravity and Galileo

Even though Sir Isaac Newton is famous for his Laws of Motion, Galileo studied how gravity affected motion long before Newton did. He didn’t have a good clock or watch with a second hand or any idea about a stopwatch. He used his pulse or a water clock that has a bowl of water with a tiny hole so the water drips out at a steady rate.

Galileo did the best he could with the equipment he had and did write down laws of motion very similar to those later written down by Newton. He was the first scientist to test some ideas people had believed for years and never thought to test.

Like Galileo we will be using the force of gravity for several Projects. We have used it for the Projects we’ve already done. So we will take a closer look at gravity and some ways it works and things that affect it.

This Project works much better with two people doing it.

Question: What are two things Galileo discovered about gravity?

Materials:

2 balls alike in substance, size and weight

2 balls alike in size [Use solid balls] but different in weight [at least double]

Grooved ramp at least a meter long

Procedure:

Look over the two balls alike in size but different in weight

Mass the two balls

You will drop the two balls from the same height at the same time

Predict which option will be true and why you think so:

1) The heavy ball will fall faster

2) Both balls will fall at the same speed

3) The lighter ball will fall faster

One person drop the balls from the same height at the same time while the other person watches to see which option is true.

Dropping two balls at the same time is harder than it sounds. Using one hand to hold and release both balls worked the best for me.

Try dropping the balls from different heights

Like Galileo we will be timing how fast a ball or car moves when pulled by gravity

Look over the two balls alike in size, substance and weight

When you use a stopwatch, you click it on when the ball or car begins to move and click it off when a certain distance is covered.

Drop one of the balls from a meter high

Could you click a stopwatch on and off in that time?

Set up the grooved ramp so one end is one meter high

I got a large piece of cardboard and folded it double to make a stiff ramp. It had to be taped to keep the folded parts together.

One ball will run down the ramp while the other drops the same height to the floor

Predict which option will be true and why you think so:

1) The ball dropping straight to the floor will drop fastest

2) Both balls will fall to the floor at the same time

3) The ball going down the ramp will get to the floor first

One person holds a ball at the end of the ramp and one over the floor at the same height

That person lets the balls go at the same time while the other person watches to see which option is true

Observations:

Describe the two balls:

Mass of Ball 1:

Mass of Ball 2:

Write down your prediction and reason for choosing it

Describe what happens when the two balls are dropped:

A heavy and a light ball fall together. Gravity pulls on both the same.

Explain why you can or can’t use a stopwatch to time how fast the ball drops:

Describe the two balls:

Write down your prediction and reason for choosing it

Describe what happens when one ball drops straight down and the other goes down a ramp:

Conclusions:

What forces are acting on the two balls as they fall when you drop them?

Which force is the most important? Why do you think this?

Does mass seem to matter to this force? Why do you think so?

What forces are acting on the two balls, one dropped and one on the ramp?

The ball going straight down got to the floor long before the ball rolling down the cardboard ramp even though gravity was the force pulling on both.

Which force seems to matter the most? Why do you think so?

Does distance traveled seem to matter to this force? Why do you think so?

What do you think would happen if the ramp were more level? Try it and find out.

Why do you think this is the case?

What do you think would happen if the ramp were steeper? Try it and find out.

Why do you think this is the case?

Do you think it is possible to use a stopwatch to time a ball going down a ramp? Why do you think this?

What I Found Out

I had to use a ping pong type of ball for my light ball and a rubber ball for the heavy one. It seems easy to think the heavier ball will fall faster because it is heavier. I can’t really predict this because I know what will happen.

When the balls dropped, both dropped straight to the floor. They hit the floor at almost the same time. I found I had to have both balls in one hand to be sure they dropped at the same time.

Gravity was pulling the balls down. Air was pushing up on the balls like it did the sheet of paper but the balls were too small and heavy for the air to push hard enough to slow them down.

Gravity doesn’t seem to care about mass as the balls hit the ground at the same time. It pulls the balls down very fast, faster than I could start and stop a stopwatch.

When I set up my ramp, I thought the two balls would hit the floor at the same time even though one ball had to travel much farther. Gravity was pulling the same on both so they should fall at the same speed.

Thinking it over now I can see the ball going down the ramp would have to get to the floor after the ball dropped straight to the ground. This is what happened. Changing the slope of the ramp made the ball take more time on lesser slopes and shorter times on steeper ramps.

Gravity does pull the same on the two balls but the distance does matter. Since a ball travels down a ramp more slowly than being dropped, I think I could time it with a stop watch.

# Physics 4 Vectors

Forces hold things in place and make them move. Some of the forces we can see. Others we know are there but can’t see. We need a way to show all of these forces. That is what vectors do.

Question: How do vectors show forces?

Materials:

Paper

Pencil

Ruler

Procedure:

Open your Journal and write Project 4

Remember Project 1 where the block sits on the table

Draw a table with legs sitting on the floor

Your drawing doesn’t need to be fancy. A simple set of boxes will work like this will work fine.

Draw the block sitting on the table

Gravity pulls down on the block so draw an arrow pointing down from the block

Gravity pulls down on the block so it sits on the table. The vector arrow points down.

Note: Gravity always points toward the center of the Earth which is usually down

If only gravity was pulling on the block, it would fall to the ground so some force is pushing back on the block. The table is pushing back so draw another arrow next to the other arrow but pointing up.

The table pushes back against the block just as hard as gravity pulls it down so a vector arrow the same size pointing up is added to the block.

How long should this arrow be? Vectors show speed and direction. We are not measuring speed but only showing direction in this Project.

Gravity pulls down. If the arrow pointing up is longer showing greater force, there would be more force pointing up than down. The block would float up off the table. It didn’t so the arrow isn’t longer than the gravity arrow.

If the arrow is shorter than the gravity arrow, the force of gravity would be greater than that of the table. The block would pull through the table and fall to the floor. It didn’t so the arrow isn’t shorter.

The arrows must be the same length as the forces are equal and opposite to each other.

Since the table is not floating away, gravity is pulling down on the legs so a vector arrow pointing down is put in each leg.

Since the table isn’t floating away, gravity must be pulling down on it too. Draw vector arrows for gravity to hold each table leg on the floor.

The floor pushes up against the table legs just as hard as gravity pulls down on the legs so the arrows are the same length as those vectors but pointing up.

Since the table isn’t sinking into the floor, the floor is pushing back against the table legs. Draw those vector arrows.

A vector arrow showing the push on the block is added aimed at the block which was the direction of the force.

Next remember what happened when you pushed on the block. Your finger was a force acting on the block. Draw a vector arrow for that force.

Did the block move? Which way did it move? Since the block moved, there was no force pushing back against your finger so there will be no arrow.

Every pair of force vectors have the arrows equal and opposite except for the last pair. The pushing force arrow must be longer than the block resistance force arrow for the block to move.

Now wait a minute! When I pushed against my block of wood, the end of my finger flattened so the block did push back. But the block moved so the force the block pushed against my finger was much less than the push my finger gave the block. I will draw a little arrow from the block toward my finger.

Paper airplanes are fun to fly. They fly and fall because of forces pushing and pulling on them. Those forces can be drawn as vectors.

Now let’s draw vectors for a paper airplane:

Draw the airplane flying

What force made the airplane fly?

You threw it so you exerted a force on it. Draw that arrow pushing the back of the airplane.

Throwing a paper airplane pushes it forward so the vector arrow pushes against the tail end.

Is gravity acting on the airplane? Gravity acts on everything on Earth so draw an arrow pointing down for gravity.

Like the sheet of paper, air pushes up on the wings of the paper airplane so the vector arrow points up toward the wing.

What is pushing up on the wings to keep the airplane up? Air pushes up.

Does the air keep the airplane up all the time? It didn’t keep mine up. So there is an arrow for the air pushing the wings up but it is less than the gravity.

The paper airplane doesn’t fly forever so gravity pulls down on it which the vector arrow shows.

Where would the arrow for the fan pushing the airplane go? Draw it in.

Notice that this arrow is with the one from you throwing the airplane so the two add up.

When the air from the fan pushes the paper airplane, the vector arrow pushes against the airplane’s tail adding to the thrust vector from you throwing it.

Where would the arrow go for when the fan pushed against the airplane? For my airplane it would be the same length as the one for throwing the airplane because I did see it stop my airplane once.

When the air from the fan blows against the paper airplane, the vector arrow must point toward the airplane.

This last set of drawings shows one way vectors help a physicist understand the forces acting on an object. When forces act together, they add up. When forces act against each other, they cancel each other out.

Another way vectors show how forces work is shown with the car going down the ramp.

Draw the ramp with a car on it.

The car is racing down the ramp so the vector arrow goes down the ramp. Or does it?

The car is moving down the ramp so the vector arrow points down the ramp but is this correct?

Gravity is pulling the car down but gravity pulls straight down. So there should be an arrow pointing down from the car.

Gravity pulls down on the car so a vector arrow points down from the car.

But the car moved down the ramp. So there is another arrow from the tip of the gravity arrow to the ramp spot where the car will be after a certain amount of time.

The gravity arrow and the forward arrow meet at the vector arrow on the ramp’s point as the two add up to that vector.

In this case vectors show the movement of the car is made up of two different vectors, one pulling down and one pulling across.

Vectors usually show both direction and acceleration. They are a way to see how forces add and subtract from each other so you can tell where an object will go when several forces push or pull on it at the same time.

For now the accelerating force we will work with will be gravity. The next Project will look at some ways gravity pulls objects down.

# Physics 3 First Law of Motion

Perhaps you have noticed especially in Project 1 that something sitting on a table or anywhere does not move unless some force makes it move. That can be a contact force like a push or a pull. It can be a non contact force like gravity, magnetism or electricity.

A man named Sir Isaac Newton wrote this down as his First law of Motion:

An object at rest remains at rest as long as no net force acts on it. An object moving with constant velocity continues to move with the same speed and in the same direction as long as no net force acts on it.

Question: How does Newton’s First Law of Motion work?

Materials:

Small car

Meter long smooth board 15 cm wide or car track

Wood block 1 cm x 1 cm x 15 cm (The height should be the height of the car hood.)

Tape

Several thick books

Ruler

Penny and nickel

Procedure:

Open your journal and write the name of the project. Copy the table.

Keeping a Journal of all of the Projects makes it easy to look up previous Projects.

Tape the small wood block across one end of the long board

The block is attached at the end of the board. Why is the block only as high as the car hood? Would a higher block change your results?

Draw a line across the other end of the board 1 1/2 times the length of the car from the end

The starting line is drawn across the board. Why is drawing the line important? Would starting the car at a slightly different place each time change the results?

Put books under the other end of the long board so the line is 10 cm off the floor [I put the line across the edge of the book so it was always in the same place.]

The car rolled down the ramp at 10 cm high then bounced off the block to a stop.

Set your car at the line and let it run down the ramp several times (If your car does not go straight down the ramp, get another car that does go straight down the ramp.)

Balance a penny on the roof of your car, set it at the line and let it go down the ramp

Measure from the block to where the penny lands and record it in the table

The penny flew around 12 cm from the car on the 10 cm high ramp.

(If the coin rolls off, don’t count that trial run but do another until the coin lands flat.)

Repeat this with the penny two more times

Repeat this with the nickel three times

Raise the line to 15 cm off the floor

Repeat with the penny three times

Repeat with the nickel three times

Raise the line to 20 cm off the floor

Repeat with the penny three times

Repeat with the nickel three times

Observations:

Describe what happens when the car alone goes down the ramp

10 cm

Describe what happens when the penny is on the car when it goes down the ramp

Describe what happens when the nickel is on the car when it goes down the ramp

15 cm

Describe what happens when the penny is on the car when it goes down the ramp

The car went faster down the ramp, hit the block at the end and bounced back then went to the block and stopped.

Describe what happens when the nickel is on the car when it goes down the ramp

20 cm

Describe what happens when the penny is on the car when it goes down the ramp

Describe what happens when the nickel is on the car when it goes down the ramp

Analysis:

An average is found by adding the different values (the 3 distances) then dividing by the number of values (3)

Find the average distance the penny goes for each board height

The distance to the penny doubled when the ramp was raised up to 15 cm.

Record the averages in the table

Find the average distance the nickel goes for each board height

Record the averages in the table

Draw a line graph of average distance against board height for the penny and nickel

Conclusions:

What force makes the car roll down the ramp?

The little car really roared down the ramp when it was raised to 20 cm high. It hit the block hard bouncing off the ramp and onto the table.

What force stops the car?

Why don’t the penny and nickel stop with the car?

The penny went over 30 cm all three times when the ramp was raised to 20 cm. It rolled across the table several times too so I had to redo the runs.

Why do the penny and nickel travel differently for the same distance?

Why don’t the penny and nickel travel the same distance all three times?

What stops the penny and nickel?

What do you think would happen if you raised the ramp another 5 cm? Try it and find out.

How does Newton’s First law of Motion apply to your results?

What I found Out

Each time I raised the ramp, the car went faster. The coins went farther for each higher ramp. Gravity pulled the car down the ramp.

When the car went down the first ramp by itself, it rolled faster as it went down. When it hit the block on the end, it bounced back and rolled off the ramp.

The penny sat on the car hood. When the car hit the block, the penny flew out onto the table. The nickel went a few centimeters farther than the penny did.

When the ramp was raised to 15 cm, the car went faster and hit the block harder, bouncing back more. Once it bounced all the way off the ramp. The penny and the nickel went farther too. The nickel still went farter than the penny.

The car went even faster when the ramp was raised to 20 cm. The penny and nickel went farther than my ruler could measure so I had to move the ruler and add the extra.

The block stops the car with a push against it. The penny and nickel are above the block so no force acts on them and they keep going.

The nickel is heavier than the penny so it goes farther than the penny. Even though I tried to start the car at the same place each time, it wasn’t exactly the same so the car ran down the ramp a little differently so the coin flew off differently.

The penny and nickel fall to the table top. Gravity makes things fall so gravity must be what stops the coins from going any further.

I couldn’t raise the ramp higher this time. My car was very flat and the coins slid off the hood. I did use a higher ramp once before. The penny and nickel went into the table top in a short distance because the car was pointed down into the table top.

Newton’s First Law of Motion says an object at rest stays at rest and an object in motion stays in motion at the same speed and direction unless acted on by another force. The car and coin were pulled down by gravity. Gravity made them go faster the longer they went down the ramp.

At the end of the ramp the force of the block stopped the car. No force acted on the coins so they kept going until gravity pulled them down to the table.

# Physics 2 Combining Forces

Last week we found out pushing and pulling were contact forces and gravity is a non-contact force. Having more than one force can change how an object moves.

Question: How can we show how forces add up?

Materials:

3 sheets of paper

Fan

Tape

Procedure:

Open your Journal and write Project 2

Hold a sheet of paper up as high and flat as you can

For this Project I held the sheet of paper out flat. How would holding it on the edge change how the paper fell? What would cause this change?

Drop the sheet of paper

Describe how the sheet of paper falls to the floor

Turn on the fan

Drop the sheet of paper like before but standing in front of the fan

Describe how the sheet of paper falls to the floor

Turn off the fan

Crumple the paper into the tightest ball you can

A paper ball has all the weight of the sheet of paper pushed together so it doesn’t catch the air and falls quickly to the floor.

Hold the paper ball up high and drop it

Describe how the ball falls to the ground

Turn on the fan

Hold the ball up like before and drop it in front of the fan

Describe how the ball falls to the floor

Fold a piece of paper into the first paper airplane (Directions are below.)

Airplane 1 has big wings with a short steep nose that doesn’t go through the air very well.

Fold a piece of paper into the second paper airplane.

Fly both paper airplanes several times to find out how and how far each kind flies

Airplane 1 has big wings. Throwing it the wings hold it up but it doesn’t fly forward well instead it acts more like the sheet of paper and settles down to the floor.

Turn on the fan

Fly each paper airplane toward the fan several times to find out how and how far each kind flies toward the fan

Throwing airplane 1 at the fan makes the airplane turn aside.

Fly each paper airplane away from the fan several times to find out how and how far each kind flies away from the fan

Airplane 1 is clumsy with its large wings but the wings catch the air from the fan and it floats farther until the breeze is mostly gone dropping the airplane to the floor. This is when the force of throwing the airplane and the force of the air add up.

Observations:

Describe how the sheet of paper falls to the floor

1) Plain

2) In front of the fan

A sheet of paper has a big surface to catch the air blown by the fan.

Describe how the ball of paper falls to the floor:

1) Plain

2) In front of the fan

Describe how the airplane flies without the fan blowing

Airplane 1:

Airplane 2:

Describe how the airplane flies toward the fan

Airplane 1:

Airplane 2:

Airplane 2 hits the air from the fan and turns aside. The force of the air goes against the force of throwing the airplane.

Describe how the airplane flies away from the fan

Airplane 1:

Airplane 2:

Conclusions:

Why does the sheet of paper fall to the ground differently than the paper ball?

How does the fan change how the sheet of paper and paper ball fall? How do you think the fan does this?

Is this a contact or a non-contact force? Why do you think so?

Why do you think the second airplane goes down nose first?

Airplane 2 has a long nose and small wings. The weight of the nose pulls the airplane down. It flies longer if it is thrown harder.

Why do the airplanes turn aside when flown at the fan?

What do you think would happen if the fan was much bigger so the area of blowing air was bigger?

Why do the airplanes fly farther when flown away from the fan?

Which airplane is more like the sheet of paper? Why do you think so?

Which airplane is more like the paper ball? Why do you think so?

What I Found Out:

The sheet of paper didn’t fall straight to the ground. It settled going a little to the side then back again getting lower each time. When the fan was blowing the sheet of paper blew across the room as it fell to the floor.

Compare a paper ball with a sheet of paper. Which will catch more air? Why? Yet even a paper ball catches some air from the fan as it falls.

The paper ball fell straight to the ground much faster than the sheet of paper fell. When the fan was blowing, the ball seemed to fall even faster but moved a little ways away from the fan.

A sheet of paper is flat and big. A paper ball is much smaller and sort of round. The sheet of paper floats on the air so it falls slowly compared to the paper ball that falls through the air.

The fan makes the air move and push on the paper. The sheet is large and flat so it catches a lot of moving air and moves a lot. The paper ball only gets pushed a little but the edge of the moving air might push it down too as it fell faster.

The air is a contact force. I can’t see it but I can feel it pushing. If there was a lot of dust, I would see the air moving.

The second airplane has a long nose and smaller wings. If you fold the wing part down another time when making the airplane the nose would get even longer and the wings smaller. How would this affect how the airplane flew in this Project?

I like making paper airplanes but am not very good at flying them. I had to do this Project at the laundromat because there was a good fan there. I was afraid of throwing the airplanes too hard and hitting someone there. I think they would have flown much better if I had thrown them harder.

The first airplane doesn’t fly very fast. It gets slower as it goes and the back end begins to sink. Then the airplane falls to the ground.

The second airplane flies faster but the nose pulls it down and makes it crash.

Flying toward the fan both airplanes turn around the blowing air. I did finally get the first airplane to fly in the middle. It seemed to stop then go straight down.

Flying away from the fan both airplanes stayed up longer and flew straighter. The first one even seemed to lift higher at first.

Flying the airplane over the top of the fan lets the wings catch the moving air. How would this cause the airplane to fly farther?

The second airplane has smaller wings than the first one. The wings are farther back on the airplane. The nose is long and thick and heavier than the back end of the airplane. Gravity pulls on the long nose and there are no wings to hold it up so the nose falls and makes the airplane crash.

When the airplanes flew at the fan, the air pushed on them. They turned to get away from the push of the air. If the fan were bigger, the airplanes would act like the time I flew an airplane into the middle: they would stop and fall down.

When the airplanes flew away from the fan, the moving air pushed them up and carried them away like it did the sheet of paper. The air slows down as it gets father away from the fan so the airplanes would fall down.

The first airplane was more like the sheet of paper because it had larger wings to catch more moving air. The second airplane had smaller wings so it was mostly folded up tight so it would fall more like the paper ball.

Paper Airplanes

1. Fold the paper lengthwise. Make the crease sharp.

It’s important to make very tight creases for the folds. Use a thumb nail or a coin to make the folds tight.

Open the paper back up.

Fold the top corner down along the crease to make a triangle with one side along the crease.

Fold the paper so the edge is flat along the center fold.

Fold the other top corner down the same way so the paper has a triangle on the top.

This side of the triangle should be the same size as the first side.

Fold the paper back along the crease.

Fold the long side down on one side.

The paper should be folded so the edge is flat along the bottom of the airplane so the wing is folded square.

Turn the airplane over and fold the other long side down the same.

Both wings are now made. The wings need to be about the same size.

Push up these folded pieces until they are flat at right angles to the rest of the paper.

Tape the back ends together.

Tape the nose triangle ends together.

1. Fold the paper lengthwise. Make the crease sharp.

This is the same fold as for the other paper airplane.

Open the paper back up.

Fold the top corner down along the crease to make a triangle with one side along the crease.

The edge of the triangle, like for the other paper airplane must go along the center fold.

Fold the other top corner down the same way so the paper has a triangle on the top.

This triangle folds down along the center fold too. Because this is the second fold, it is harder to make the fold really tight.

Fold both sides to the crease a second time so it looks like a long triangle.

This triangle must match where the same triangle was on the other side.

Fold the paper back up on the original fold.

This fold must be even with the other side.

Tape the nose end together with one piece of tape.

Fold the wing down so the end is flat along the edge of the body fold. Do the same for the other wing.

Fold down the long side on each side.

This paper airplane is now ready to fly.

Push the side flaps up flat.

Tape the back end together with a piece of tape.

# Physics 1 What Is a Force

Be sure to start a Physics Journal to keep track of all your physics projects. Sometimes one Project will ask you to take another look at a Project you did earlier. A Journal makes this easy to do.

A physics journal doesn’t have to be fancy, just full of paper to write on. That way all or your observations are in one place, easy to find.

Physics can be very hard with lots of difficult math. But some parts of physics are much easier. Those are the ones we will be doing this year.

Physics tries to explain forces. What is a force? The easiest definition of a force is: A force is a push or a pull.

Question: What is a force?

Materials:

2 Small blocks of wood

Ball

Scale

Procedure:

Open your Physics Journal and write the Project number

In my Physics Journal I put only the Project number and question. then I list the observations, analysis and conclusions. If I did not have the materials and procedure on the computer, i would put those in my Journal too.

Set a block of wood on a table then leave the room

Left setting on a table a wood block sits there not moving.

Come back in the room and look at the block of wood

Did the block of wood move?

Push on the block of wood with a finger

Does the block of wood move?

Pushing on the wood block caused the block to move in the direction of the push.

Pull the block of wood using a finger

Does the block of wood move?

Hold the ball in your hand

Does the ball stay in your hand?

Drop the ball

What does the ball do?

Place one block of wood on the scale

Block 2 has a weight of 57.57 g. It wavered between 57.56 g and 57.57 g but finally settled on 57.56 g.

Place the second block of wood on the scale

Put both blocks of wood on the scale

Observations:

Did the block of wood move?

What happens when you push the block of wood?

What happens when you pull the block of wood?

What does the ball do in your hand?

What does the ball do when you drop it?

How much does one block of wood weigh?

Block 1 had a weight of 32.13 g.

How much does the second block of wood weigh?

How much do both blocks of wood weigh?

Analysis:

Add up the masses of the two blocks of wood

Together the wood blocks have a weight of 89.69 g.

Conclusions:

What makes the block of wood move?

Why doesn’t the block of wood float off the table?

Why does the ball sit in your hand?

A ball sits in the hand as long as it is held there.

Why does the ball drop when you let it go?

A contact force is a force you apply directly to an object. A non-contact force is a force applied to an object without touching it. Which of the forces applied to the block of wood and the ball were contact forces and which were non-contact forces? Explain why you think this.

Compare the masses of the two blocks on the scale and the two masses you added up. Do masses combine? Why do you think so.

Weight is a measurement of the pull of gravity. Do you think forces combine? Why do you think so?

What I Found Out

My block of wood didn’t move by itself. It did move when I pushed or pulled it. Pushing or pulling the block makes it move. It sits on the table because of gravity.

Pulling on the wood block caused the block to move across the table in the direction it was pulled in.

The ball sat in my hand because I was holding it until I dropped it. Then it fell down to the table. Gravity pulled the ball to the table.

This was not a bouncy ball. It fell to the table with a thud when I let go of it.

Pushing and pulling the block of wood were contact forces because I had to touch the block to make it move. Gravity is a non-contact force because it works without touching the block or the ball.

The total mass of the two blocks was 89.69g and the added mass of the two blocks was 89.69g which is the same so I think masses can be combined or added together. Gravity creates weight and is a force so I think forces can be combined.

# P27 Rock Candy

Crystals as we saw in the last Project have regular shapes. Not everything we look at as a crystal is really a crystal like sugar. Can we grow sugar crystals?

The sugar crystals are called rock candy. If you used clean string and jars, you can eat it.

Question: How do different crystals grow large?

Materials:

Sugar

Water

Measuring cups

Stove

Pan

Piece of charcoal

Salt

2 Jars

Pencil

String

Procedure:

Growing sugar crystals:

Pour 1c water into a medium sized saucepan

Heat as you stir to dissolve the sugar

Stop stirring when the sugar dissolves

Heat the solution to boiling [Be careful as it will quickly foam up and out of the pan when it boils.]

Sugar solution fills both jars. Strings hang down from pencils. The sugar crystals are supposed to form on the strings.

Cut a length of string long enough to tie to a pencil and reach to the bottom of the jar

Tie the string to the pencil

Tie a little weight to the other end [I used a tiny nail.]

Wet the string

Pour the sugar solution into the jar almost to the top

Dangle the string in the solution so it doesn’t quite touch the bottom of the jar

Set the jar aside to let the sugar crystals form [This can take a week.}

Growing salt crystals:

Put a layer of salt 1cm deep on the bottom of the jar

In two days the salt layer has a smooth salt slurry on top. The charcoal is soaked.

Add water so it is 1cm over the salt

Set the piece of charcoal on the salt layer

Set the jar aside for the salt crystals to form [This can take a week.]

Observations:

Describe the sugar solution you pour into the jar

Describe the sugar crystals each day for a week

By day two sugar crystals covered the top of the solution but none were on the string.

Describe what happens in the jar of salt and charcoal every day for a week

Conclusions:

Why do you put a weight on the end of the string?

Are the sugar crystals true crystals? Why do you think this?

In the last Project salt formed cubes as crystals. Does it form cubes on the charcoal?

Look closely for thin white patches started on the pieces of charcoal. How does the salt get on top of the charcoal?

What is happening to the salt crystals on the charcoal?

What I Found Out:

Hot water dissolves a lot of sugar. The solution gets thick. I could see swirls as I stirred.

When I stopped stirring, the solution became very clear but slightly brown in color. It suddenly foamed up and out of the pan.

Plain string floats on the sugar solution. I used a tiny nail to add weight to the string so it dangled down into the solution in my two jars. The solution was too much for one jar.

In a few hours clear sugar crystals formed across the tops of my two jars. These had some hard bubbles or foam on top.

By the next day these top layers were thick. One jar had crystals forming on the bottom. No crystals were forming on the strings.

My rock candy formed across the top of the solution and the bottom of the jar. A few crystals are forming on the string and nail.

On the third day some crystals were forming on the string and nail in one jar and the string in the other one.

Nothing seemed to happen on the first day in the jar with the salt and charcoal. The charcoal was very wet and shiny.

By the second day I could see little white spots on the charcoal. These began to look like spider webs on the charcoal. Then little mounds started building up on the charcoal.

Water and salt seep up through the charcoal. The water evaporates leaving the salt behind. After four days there are little salt piles several places on the pieces of charcoal.

These salt crystals looked entirely different from last Project. They look like stalagmites in a cave. It looks like the salt water pulls up over the charcoal and the water evaporates leaving a mound of salt behind.

Having Fun

When you set up the charcoal, put food coloring on the charcoal. You can put several drops of different colors in different places or several drops of one color in different places. How does this change the salt crystals?

Look up the Devil’s Golf Course in Death Valley. This is the charcoal set up by nature on a gigantic scale.

# P26 Crystals

Remember our first Projects this year, matter can be gases, liquids or solids. Just like water, many substances have melting points and boiling points. Metals like iron have very high melting and boiling points so we see them as solids. Gases like oxygen have very low melting and boiling points.

The difference between gases, liquids and solids is how much energy an atom or molecule has. Remember our Project melting water. When you are lying down sleeping, you don’t need much energy. The same is true of solid substances.

When you get up and start walking around, you need more energy to keep awake and moving. Liquids are like that. The atoms and molecules need enough energy to move around.

Take off running and jumping around and you need lots of energy. Gases are like that. The atoms and molecules have lots of energy and move around very fast.

What Is a Crystal?

A crystal is a solid but not just any solid. Glass is a solid but not a crystal. How do you tell?

When glass breaks, the pieces are different shapes and sizes. Safety glass seems to break into similar shapes but it has special substances and coatings on it to make it do that. Plain broken glass has lots of sharp points and can cut you badly.

Shake some salt out on a saucer and examine the bits with a magnifying glass. Many of the pieces are squares or chipped squares. Salt forms crystals.

Shake out a pinch of canning salt and little cubes are easily seen. Salt or sodium chloride forms cubic crystals.

Shake some Epsom salts out on a saucer and examine the pieces with a magnifying glass. These pieces are not squares but they do have the same shape.

Both salt and Epsom salts or magnesium sulfate form crystals. In a crystal all the ions, atoms or molecules in the solid are arranged in an orderly, repeating three dimensional pattern called a crystal lattice.

Question: What are some crystal shapes?

Materials:

Saucers or custard cups [one per substance]

Water

Salt

Sugar

Magnesium sulfate [Epsom salts]

Copper sulfate

Alum [Potassium aluminum sulfate]

Sodium carbonate [washing soda]

Magnifying glass

Procedure:

Put two pinches of a substance in a custard cup

Examine the substances with a magnifying glass

Draw the shape of some pieces

Magnesium sulfate has thick chunks when it comes out of the package.

Write down if each substance is a crystal

Add a few drops of water

Add water a few drops at a time until the substance dissolves

Use as little water as possible when making the solutions.

Set the custard cups aside to let the water evaporate

After the water evaporates, examine the solid left behind

Magnesium sulfate forms long pointed crystals when the solution dries.

Observations:

Draw the shape of each substance:

Salt:

Sugar:

Magnesium sulfate:

Copper sulfate is a pile of ground up bits in various shades of blue.

Copper sulfate:

Alum:

Even with a magnifying glass alum pieces are difficult to see as they are so small.

Sodium carbonate:

Do you think the substance is a crystal?

Salt:

Sugar:

Magnesium sulfate:

Copper sulfate:

Alum:

Sodium carbonate:

After the water evaporates, draw the shape of the solids:

Salt:

Sugar:

Magnesium sulfate:

Copper sulfate solution is slow to dry but the crystals left can be large and are an interesting shape.

Copper sulfate:

Alum:

The tiny Alum crystals are about twice the size of the ones in the container but are still too small to see well.

Sodium carbonate:

Conclusions:

Why did you decide a substance was or was not a crystal?

Salt:

Sugar:

Magnesium sulfate:

Copper sulfate:

Alum:

Sodium carbonate:

Were your predictions correct? Why do you think so?

Salt:

Sugar:

Magnesium sulfate:

Copper sulfate:

Alum:

Sodium carbonate:

Why was as little water used to make the solutions as possible?

Why not heat the solutions? Try it and find out.

What I Found Out:

It was very hard to see any shapes with the magnifying glass. My table is white and so were most of the substances so I put a piece of colored paper under the custard cups.

The salt bits were all the same size and looked all alike so I think it is a crystal. The sugar bits seemed to have more than one size but the shapes were similar so maybe it is a crystal too. The magnesium sulfate had different sizes but all the same shapes so it is a crystal. The copper sulfate was too small to tell. I will guess it is a crystal. The alum was even smaller than the copper sulfate but every piece seemed to be like every other piece so it must be a crystal. The sodium carbonate looked like crunched up rock. I don’t think it is a crystal.

Straight out of the package sugar is a pile of little pieces.

The crystals are: salt, sugar, magnesium sulfate, copper sulfate and alum. Only the sodium carbonate is not a crystal.

Some of my predictions were wrong.

Salt did form little cubic crystals. Magnesium sulfate formed long crystals. Copper sulfate formed lovely blue fat parallelogram crystals. Alum formed little cubic crystals still hard to see. I was right about these.

The sugar solution dried but never formed crystals. Instead it formed a clear flat sheet on the bottom of the custard cup. It is not a crystal and I thought it might be. It makes me wonder why it is in the package.

Sugar dissolves in water easily disappearing into solution. The water leaves. The sugar bits don’t. Instead a clear film dries onto the custard cup.

The sodium carbonate formed square crystals plus other stuff. Washing soda must have more ingredients than sodium carbonate. The sodium carbonate does form crystals.

Tucked into white smears maybe of soap are crystals of sodium carbonate.

The more water in a solution, the longer it takes for the water to evaporate. By using very little water, my solutions dried overnight.

Another way to watch crystals form is under a microscope. The heat from the light evaporates the water. The crystals formed are very small which doesn’t matter using a microscope.

Water leaves slowly with evaporation so the crystals have more time to form and they get bigger.

Next Week We’ll Grow Bigger Crystals

This takes more solution and more time. We’ll grow rock candy (sugar crystals), salicylic acid crystals and salt crystals. You will need sugar, salt and a piece of charcoal.

# P25 Aspirin Ingredients

For a long time the only pill to take when you had a headache or a fever was aspirin. Indians got headaches too. They chewed willow leaves. Why?

What is aspirin?

Get a bottle of aspirin tablets and read the label. All it says is aspirin.

Question: What is aspirin?

Materials:

6 aspirin tablets

Ferric acetate solution [boil steel wool in vinegar, filter to get the solution]

Iodine [Betadine, 7% iodine, others from pharmacy]

Rubbing alcohol

Water

Saucepan

Stove

Filter [paper towel]

Jar

Saucer

Eyedropper

Procedure:

Break 1 tablet in half

The drop of red iodine soaks into the aspirin tablet and turns blue.

Put a drop of iodine on one half

Record what happens

Put a drop of ferric acetate on the other half

The drop of ferric acetate sits on the aspirin tablet with no color change.

Record what happens

Put the 5 aspirin tablets in the pan

Cover them with water

Boil until most of the water is gone [Not all!]

As the water boils, smell the steam being given off

Let it cool

Add 1/4c alcohol to the pan and dissolve the solution in the pan

Be sure to get the white precipitate into the filter with the liquid alcohol solution.

Filter the solution into a jar

Test the chemicals left in the filter with a drop of iodine

Record what happens

Put five drops of solution from the jar in two places on the saucer

A drop of red iodine stays red in the filtrate.

Add a drop of iodine to one spot

Add a few drops of ferric acetate solution to the other spot

Record what happens

Observations:

Describe what happens when

Iodine is put on the tablet

After the drop of ferric acetate soaked into the aspirin tablet, there was no color change and the tablet crumbled.

Ferric acetate is put on the tablet

Describe what the steam smells like

Describe what happens when iodine is added to the filter remains

Describe what happens when iodine is added to the solution

Describe what happens when ferric acetate is added to the solution

Conclusions:

Iodine turns dark purple to black when added to starch.

Is starch in an aspirin tablet? How do you know?

Starch is found in potatoes. Does eating a potato stop a headache?

Is starch the part of an aspirin tablet that stops a headache?

A drop of reddish ferric acetate turns blue when added to the filtrate from the aspirin.

Ferric acetate turns dark blue when added to salicylic acid.

Does an aspirin tablet contain salicylic acid? How do you know?

Is the salicylic acid the part of an aspirin tablet that stops a headache?

What ingredients are in an aspirin tablet?

What I Found Out

The ferric acetate solution is reddish in color. The drop sat on the broken part of the aspirin tablet then soaked in. It showed no color change. The tablet crumbled into wet grainy powder.

The iodine solution is dark red. It was hard to see what was happening at first. Once the drop soaked into the tablet, blue coloring remained on the edge.

The aspirin tablet contained starch. I don’t think eating a potato helps cure a headache. It doesn’t help mine. So I don’t think the starch is in the aspirin tablet to stop a headache.

I added water to the 5 tablets in the pan. They crumbled then dissolved. The water boiled. The steam smelled faintly like vinegar so I think the tablets contained acetic acid. When only a little water was left, it looked cloudy and thick.

Aspirin first dissolves then forms a white mass and clear spears of crystals when boiled then cooled.

I left the pan and contents to cool. When I looked again, there was a ring of straight crystal looking stuff around the bottom of the pan. It was white.

The alcohol didn’t dissolve the white stuff in the pan. Instead it clumped together and fell out into the filter in a lump. The liquid that went into the jar was slightly cloudy.

Red iodine solution turns dark purplish blue when dropped onto the white substance filtered out indicating starch.

The white lump turned the iodine solution blue. The liquid didn’t change the iodine solution, it stayed reddish.

The ferric acetate solution turned dark blue in the liquid. This would indicate that salicylic acid was in the liquid. Aspirin tablets contain salicylic acid which is what stops a headache.

Aspirin is made from starch, salicylic acid and acetic acid [vinegar]. Other than the smell, it takes more advanced chemistry than we are doing to test for acetic acid. We can and did test for the presence of salicylic acid.

Willow bark and leaves contain salicylic acid. This was the basis for simple home remedies for headaches and fever of chewing the leaves and twigs.

If you boil some twigs and leaves for five minutes, you can test the liquid with ferric acetate. I had added this to the Project then realized my willow trees still have no leaves on them.

After chemists isolated the salicylic acid and found combining it with acetic acid made it more effective, aspirin tablets were developed. The starch was added because so little of the salicylic acid was needed. And the starch made it easy to press the powder into tablets.

# P24 Flame Tests

Have you ever burned the comics page from a newspaper? The flames have different colors. Where do these colors come from?

Note: This Project uses an open flame. Be sure to tie back long loose hair and sleeves. Handle the long wire carefully as the end in the flame will be hot and the heat will travel up the wire. If the wire is only a foot or so long, use a hot pad.

Question: How can flames be in colors?

Materials:

Boric acid [from a pharmacy]

Cream of tartar

Salt

Calcium chloride [Ice Melt]

Copper sulfate

Wire hangar or long piece of wire [18 inches]

Or 4 wood splints [long thin bits of wood]

Saucer

Water

Gas stove

Procedure:

With the wire:

Take the long piece of wire and make a small loop in the end

[You can fold the end back so the folded end is close to the wire.]

Hold the folded end of the wire in the flame on the stove until it shows red

Set it aside and let it cool

Boric acid contains boron. it burns with a spring green flame.

Put a pinch of boric acid powder on the saucer

Dip the loop in water then in the powder

Hold the boric acid in the flame until it has all burned

Set the wire aside and let it cool

Clean the wire

Repeat with the other chemicals but do the salt last

With the Wood Splints:

Dissolve each of the four chemicals in water

Label the splints with the name of one chemical

Soak a wood splint in its solution for 30 minutes

Let the splints dry

Hold the soaked end of the splint in a flame

Observations:

Describe what happens when you burn each kind of powder

The Ice Melt should only have the metal calcium in it but my sample had a pink and an orange flame so it had another metal in it.

Conclusions:

Where would the molecules put this extra energy?

Why would copper sulfate have two colors of flames?

Copper sulfate starts with a green flame then has a yellow one. It contains two metals: copper and sulfur.

My Ice Melt or calcium chloride had a small pink flame and a bigger yellow flame. Why would I think my Ice Melt was not pure calcium chloride?

What else might be in the Ice Melt?

What I found Out:

I used the looped wire. I have used the splints before and I think they may be easier.

The boric acid had a lovely spring green flame.

The calcium chloride or Ice Melt started with a pink flame but soon had an orange flame.

Cream of Tartar contains the metal potassium. It burns with a white flame tinged with lilac.

The Cream of Tartar is a potassium compound. It had a white flame with a lilac tinge.

The copper sulfate had a green flame and a yellow flame.

Sodium chloride or salt had a large orange flame that lasted long after I thought it was done.

Salt contains the metal sodium which burns with a large orange flame.

Heat is a form of energy so adding heat is adding energy to a chemical. The chemical has only a few places to put that energy. One is in the bonds between atoms. The other is in its electrons.

Copper sulfate has two metals in it: copper and sulfur. The copper has a green flame and the sulfur has a yellow flame.

My calcium chloride had two colors of flames like the copper sulfate did so it must have two metals in it. Calcium is a metal. Chlorine is not. The orange flame was like that for salt so I think my Ice Melt had salt as well as calcium chloride in it.

Why Are the Flames Colors?

When we did the electron shells, we were looking at electron energies. Each shell has a certain energy. Normally electrons sit in the shells with the least energy.

Heat added energy so the electrons had more energy and moved into higher electron shells. But the electrons prefer their lower energy places so they give up the extra energy and go back to their original place.

The energy given off can have the energy of a particular color of light. This is what you see when the flames are in color.

# P23 Chemical Energy

Transition metals do a number of interesting things. Making compounds in more than one way is what we looked at last Project. Another fun one is making colors with metals. We’ll do that next Project.

This Project we’ll explore why the metals can make those colors. It has to do with energy.

What is energy?

Energy is how a substance causes change in its surroundings such as in a chemical reaction. These changes are done through heat or work.

Energy can be stored up. This is called potential energy.

An example of potential energy is holding a book up off the floor or table. It isn’t doing anything.

However, when you drop the book, it falls releasing all that potential energy from gravity until it hits the floor or table. Then the energy is given away to the floor or table mostly as heat.

Where do atoms and molecules store energy?

An atom stores energy in its electrons and their orbitals. A molecule stores energy in the electrons it shares with another atom. Different orbitals can store up different amounts of energy.

Note: This Project works best done by two people. One person reads the thermometer. The other person times the readings and writes them down.

Question: How does a molecule store energy?

Materials:

Ice [This goes faster if the ice is in smaller pieces.]

Quart Sauce Pan

Thermometer

Stirring spoon

Stove

Clock or watch with a second hand or showing seconds

Procedure:

Set up your Observation sheet with times from 0 [starting T] to 25 minutes

Ice volume decreases when it turns into water so make sure you pack in all the ice you can. The thermometer can’t touch the bottom of the pan.

Pack the pan with ice to the top

Stick the thermometer in the middle but not touching the bottom of the pan

After a minute, record the temperature

It takes at least a minute before the thermometer liquid stops moving so you can read the temperature.

Put the pan on the stove over low to medium heat

Note: Do not change the heat!

Record the temperature every 15 seconds until the water reaches 120 degrees Fahrenheit

Stir the ice before taking a temperature especially after water is in the pan

The ice was almost to the top of the pan. The water barely half fills it.

Record what is happening in the pan [all ice, mostly water etc.]

Observations:

Have a column of times starting with 0 to 25 minutes

Go up by 15 seconds for five minutes

Leave room for a second column to write down the temperatures

 Time (sec.) Temperature Looks 0 15 30 45 1min 1min 15 1min 30 Etc.

Analysis:

Draw a graph with time on the x-axis [horizontal] and temperature on the y-axis [vertical]

Conclusions:

Was the amount of heat added constant? How do you know this?

Did the temperature go up the same amount all the time? How do you know this?

What was happening when the temperature did not go up the same each time?

How was the heat energy being used by the water molecules during this time?

Does ice or water have more energy in its molecules? Why do you think this?

When water gets hot enough, it changes to gaseous water vapor. What do you think the temperature will do as this change occurs?

What I Found Out:

I had to do everything by myself. I could tie my thermometer up so no one had to hold it.

In the beginning the entire pan was full of ice. It had lots of air pockets between the ice cubes. The temperature was 31 degrees.

Once heat was started, water started to appear in the pan. But the temperature stayed at 32 degrees for over 4 minutes.

Make a time column before beginning the Project to make recording the temperatures easier.

After 7 minutes there was enough water in the pan for the ice cubes to float. The temperature would seem to go up but would drop again as soon as I stirred up the ice and water.

Once most of the ice had melted, the temperature started going up. It went up about 2 degrees each reading. All the ice was gone at62 degrees almost 16 minutes after I started heating the ice.

Temperatures were not always on the curve once the mix was water and ice in the pot. the water wanted to get warmer but the ice wouldn’t let it.

Since I didn’t change the amount of heat from the stove, I think about the same amount of heat was added all the time.

The temperature was not going up the same all the time. As long as there was lots of ice to melt, the temperature stayed the same or went up only a little.

The heat must be used to melt the ice instead of making the water or ice warmer. That means the water has more energy in it than the ice did.

While the ice changed to water, the temperature stayed the same. When water boils into steam, the water is changing from liquid to gas. I think the temperature will stay the same until all the water is vapor.

# P22 Iron Is Different

When we looked at the Periodic Table, we looked at the first two columns and the last seven columns. There were a lot of elements we overlooked.

What are all these elements?

They are the transition metals.

Why are they called transition metals? A transition is a change from one thing to another. These metals change.

The Periodic Table of Elements is an organized way for chemists to keep track of the one hundred fifteen known elements.

When we looked at how elements became compounds, we used the Octet Rule. Each atom wanted to become like the nearest Noble gas with two s electrons and six p electrons in its outer shell.

Elements that gave electrons away were metals. They were found on the left of the Periodic Table.

Transition metals are also on the left of the Periodic Table. They also tend to give their electrons away when they form compounds.

The big difference is that transition metals have a third kind of orbital called the d orbitals. Ten electrons fit into the d orbitals. But metals don’t fill them the same way the s and p orbitals filled.

Iron has the symbol Fe. In Latin iron is ferrum which is where the symbol came from. It is atomic number 26. Can you find it on your Periodic Table?

Iron is used for lots of things because it is strong. It holds up tall buildings. It holds pieces of wood together. It is used in pots and pans for cooking.

Iron reacts with many other elements. It reacts in more than one way. This makes it different than the other metal columns we looked at.

Question: How does iron react?

Materials:

Steel wool

Vinegar

Ammonia

Hydrogen peroxide

Stove

Pan

Jar

Saucer

Eyedropper

Procedure:

Put a small piece about golf ball size in a small pan

Pour in enough vinegar to cover the steel wool

Iron in the steel wool reacts with the vinegar to form ferric acetate.

Heat the vinegar and steel wool to boiling and simmer for five minutes

Let it cool

Filter the liquid into the jar

After the solution cools, it is poured through a filter to separate the pieces of steel wool.

Label the jar Ferric Acetate

Put five drops of ferric acetate on the saucer

Use the eyedropper to put five drops of ferric acetate on the saucer. Remember to rinse the eyedropper out between solutions.

Mix and observe carefully

Adding ammonia to the ferric acetate makes ferrous hydroxide, a green solid.

Add five drops of hydrogen peroxide

Mix and observe carefully

Put five drops of ferric acetate in another spot

Add five drops of hydrogen peroxide

Mix and observe carefully

Observations:

Describe the ferric acetate solution

Describe what happens when ammonia is added to ferric acetate

Describe what happens when hydrogen peroxide is added to the mixture

Adding hydrogen peroxide changes the ferrous hydroxide to ferric hydroxide.

Describe what happens when hydrogen peroxide is added to ferric acetate

Adding hydrogen peroxide to ferric acetate makes brick red ferric hydroxide.

Conclusions:

Does iron react the same way with ammonia and hydrogen peroxide? Why do you think so?

Which way does iron prefer to react? Why do you think so?

The ferrous hydroxide was a solid precipitate and the ferric hydroxide is too.

When iron rusts, it reacts with oxygen. Is this reaction more like the ammonia or more like the hydrogen peroxide reaction? Why do you think so?

What I Found Out:

The ferric acetate solution is a clear liquid with a slight white tinge. Five drops on the saucer were only seen as a clear liquid spot.

As soon as the ammonia was added, yellow green flecks appeared. The flecks were little bits so they must be a precipitate.

When I added the hydrogen peroxide, the flecks turned brick red. They did not dissolve.

Hydrogen peroxide added to ferric acetate turned the liquid clear brick red. There were no flecks so no precipitate was formed even after it sat for some time.

Changing ferric acetate directly to ferric hydroxide leaves it in solution. Going through ferrous hydroxide first leaves it a precipitate.

Ferric acetate definitely reacts differently with ammonia and hydrogen peroxide. The ammonia forms a green precipitate. The hydrogen peroxide forms a red compound.

Iron seems to prefer to react to form the red compound as the green compound changes to red. Rust is red so iron reacts with oxygen like it does with hydrogen peroxide.

How Iron is Different:

Iron reacts in two different ways. In one way it gives up two electrons. In the other it gives up three electrons.

When iron reacts with ammonia, it gives up two electrons and forms ferrous hydroxide. This has that greenish color.

When iron reacts with hydrogen peroxide, it gives up three electrons and forms ferric hydroxide.

When you see an iron compound formula, how do you know if it is ferrous or ferric?

Ferrous hydroxide is Fe(II)OH2. Ferric hydroxide is Fe(III)OH3. Notice the different numbers of hydroxide groups.

Most of the transition metals can react in more than one way. You can always tell how many electrons the metal gave up by looking at that number in the parentheses in the chemical formula.

# P21 Water of Hydration

Last week we found some compounds have water molecules traveling with them. How many water molecules? Not all hydrates are the same. Let’s find out about copper sulfate.

If you don’t have any copper sulfate, you can use sodium carbonate [washing soda] instead. The directions would be the same. Your answers would be different.

Before we begin you need to know some things.

• One is that we will be working with an open flame. Be sure to tie hair back and keep your sleeves away.
• Next please remember that a hot can and a cold can look much the same but don’t feel the same. Use the tongs for handling the can.

Question: How much water is in copper sulfate hydrate?

Materials:

Copper sulfate

Small clean empty can [cat food, tuna, no plastic coating inside]

Tongs

Scale

Stove

Procedure:

Mass the empty can

Finding the mass of the empty can is important.

Put in 5g copper sulfate

Getting exactly 5g of copper sulfate is difficult. I ended up with 4.99g.

Turn the stove on very low

Heat the copper sulfate over the flame

Shake the copper sulfate a little as it heats until all the blue color is gone

Let the can cool

Mass the can and heated copper sulfate

Observations:

Describe the copper sulfate

Mass of copper sulfate and can

Mass of can

Describe what happens to the copper sulfate as you heat it

Low gentle heat dries the hydrate without burning it or making it pop out of the can.

Mass of can and heated copper sulfate

Analysis:

Find the molar mass of copper sulfate [CuSO4]

Find the molar mass of water [H2O]

Find the mass of water in the hydrate [Subtract the final mass from the starting mass.]

Divide the mass of heated copper sulfate by the molar mass to find out how many moles of copper sulfate there are.

Divide the mass of water lost by the molar mass of water to find out how many moles of water were in the hydrate.

Compare and reduce to lowest terms the moles of copper sulfate to moles of water to find how many water molecules attach to a mole of copper sulfate. [round the proportion to whole numbers.]

Conclusions:

Why do you need to shake the copper sulfate as it heats?

Why are the molar amounts so low?

Why does this not matter finding a proportion?

Once the copper sulfate hydrate is heated until all the water is gone it is a grayish powder. The mass has dropped to 3.23g.

What I Found Out

Copper sulfate is a coarse blue powder. Looked at closely, it has an interesting crystal shape but most are broken in the powder.

When I started heating the copper sulfate, the blue got deeper and looked wet. Bits of the powder sizzled. Other bits popped and shot up from the bottom of the can. The color started changing.

As the copper sulfate heated, it clumped together. As it changed to a whiter color, the clumps broke up into powder again. Shaking the can from time to time helped it break up and heat all the hydrate.

The molar mass of water is 16 + 1 + 1 or 18.

The molar mass of copper sulfate is 63.5 + 32 + (4 x 16) or 95.5 + 64 or 159.5.

I started with 30.12g – 25.13g or 4.99g of hydrate.

The dry copper sulfate was 28.36g – 25.13g or 3.23g. This is .02 moles. The copper sulfate is heavy and I had only a little so the molar amount is very small.

The water was 4.99g – 3.23g or 1.76g. This is .11 moles.

The proportion is .11 moles water to .02 moles copper sulfate or 11 to 2. This would attach 5.5 molecules of water to every molecule of copper sulfate which would not happen. Why not?

Molecules can’t split up and be the same substance. A proportion compares amounts so the decimals can be moved the same number of places and keep the proportion the same.

Instead, assuming [probably correctly] that my Project had some inaccuracy in it, a proportion of 5 to 1 or 6 to 1 would be more reasonable. Copper sulfate is known to have 5 molecules of water attaching to every molecule of copper sulfate.

If you worked with sodium carbonate, I think the proportion should be 10 to 1. However I’m not certain and forgot to look it up this morning.