Physics 13 Using Rollers

Remember a simple machine doesn’t change the amount of work you do. You will still move an object the same distance. What a simple machine does is make that work take less effort. Are rollers a simple machine? What are rollers anyway?

These are not the kind girls use to curl their hair.

roller project materials

Question: How do rollers work?

Materials:

Book

String (scissors to cut it)

Rubber band

Six or seven round pencils

Procedure:

Wrap the string one and a half times around the book

measuring the string

I used a smaller book. The book could be twice as thick and this project will still work.

Cut off the piece of string

Tie a loop in one end of the string

loop in string

The loop can be an inch or a little more long. If it is less than half an inch, it will be harder to attach it to the rubber band.

Put the other end of the string through the rubber band and the loop

attaching the rubber band

The end of the string goes through the rubber band first and then the string loop.

Pull the string tight

loop around rubber band

The string loop must be pulled tightly to the rubber band so it will not slip pulling the book later.

Tie the string around the book

string around book

The string should be tied around the middle of the book so it will pull evenly across the table.

Use the rubber band to pull the book across the table

Set the book back at the beginning

spacing the rollers

The pencils should be fairly evenly placed so the book can move from one to the next without falling off.

Space out the pencils so three will be under the book and the others in front of it

Set the book on the last three pencils

Use the rubber band to pull the book across the pencils

Observations:

Describe how the rubber band behaves as you pull the book on the table

Pulling the book without rollers

Pulling the book across the table creates friction for the entire surface. Friction makes the book harder to pull.

Describe how it feels pulling the book on the table

Describe how the rubber band behaves as you pull the book across the pencils

Describe how it feels pulling the book across the pencils

Conclusions:

Assuming you pulled the book the same distance both times, did you do the same amount of work? Why do you think so?

Was it easier to pull the book on the table or on the pencils?

rollers under book

The pencils roll as the book is pulled over them making the name rollers apt.

What did the pencils do under the book as it went over the top of them?

Why would the pencils be called rollers?

Can you think of another name for a roller? What is it?

What I Found Out:

My book had a slick book cover on it so it pulled across the table easily. The rubber band stretches out at first then sprang back once the book started moving. The book dragged a little on the table.

The rubber band barely stretched before the book started pulling over the pencils. It moved very fast over the pencils. The book didn’t drag at all.

used roller pencils change spacing

The pencils do roll but some roll better than others. They are not attached to the book so they bunch up losing their spacing.

Since work is the distance times the mass, I did the same amount of work. The mass of the book and the distance did not change with and without the pencils.

What did change is how easy it was to pull the book over the pencils. The pencils turned and rolled under the book.

The pencils could be called rollers because that is what they did: rolled. Something else that rolls is a wheel.