You are going to visit a friend and run up to the porch. How are you going to get onto the porch? You can jump up or you can walk up the steps.
Jumping up may be more fun. Walking up takes less effort. Those stairs are one kind of inclined plane.
Question: How does an inclined plane work?
3 Boards or pieces of stiff cardboard 10 cm wide and 0.5 m, 1 m and 1.5 m long
3 Bricks or 3 books about 5 cm thick
Block with loop
Set up the pile of books
Measure the height of the pile of books
Stand the block next to the pile of books
Use a spring scale to lift the block onto the books recording the force in grams
Remove the block
Measure the length of the boards
Lean the short board on the pile of books to form an inclined plane or ramp
Set the block just on the edge of the board
Use the spring scale to pull the block up onto the books recording the force needed
Repeat this for each of the other boards
Height of book pile:
Length of short board:
Length of medium board:
Length of long board:
To lift the block
Calculate the work needed to get the blocks onto the books by multiplying the force on the scale times the height of the books. This is W = Fd or Work = Force times distance.
Using a simple machine is supposed to reduce the force needed to get the same amount of work done. Now that we know how much total work is needed, we can calculate the force needed for each of the inclined planes by rearranging the formula so W/d = F or work divided by distance equals force.
Calculate the force needed for each inclined plane.
Go back to the Procedure to complete the Project
Compare the force you measured for each inclined plane with the force you calculated.
Compare the force needed for each ramp with the force needed for the others and to the force needed to lift the blocks.
What happens to the distance you must pull the block to use less force?
Would it be better to lift or use a ramp for a lightweight object? Why do you think so?
Would it be better to lift or use a ramp for a heavyweight object? Why do you think so?
What is the advantage of using a ramp?
What I Found Out:
This week I found Hailyann Workman to help me do this project. She is five and in kindergarten. She thought pulling the blocks up a ramp fun to do.
My stack of books was 15 cm tall. The scale registered 200 g lifting the blocks up. The work done was 3000 g-cm.
The short ramp was 44.5 cm long. The scale showed 150 g needed to pull the blocks up the ramp. I calculated 67.4 g-cm.
Next the blocks went up a 74 cm ramp using 100 g of force. I calculated needing 40.5 g-cm.
The long ramp was 109 cm and rough. It was hard to pull the blocks up so I taped paper onto the ramp to make it smooth. The blocks pulled up easily with 70 g of force needed. My calculated amount was 27.5 g-cm.
My measured forces were much higher than my calculated forces. Perhaps I misread the scale. My block was smooth but not slick. My ramps were not slick so there was friction.
The needed force did decrease as the ramp got longer. The medium ramp took half the force of lifting the blocks.
The distance increases as the force needed decreases.
A lightweight object can be lifted up to move it the shortest distance. A heavyweight object should be moved up a ramp. This takes more distance but requires less force and is easier on you than lifting something heavy.
A ramp is a way to decrease the force needed to move an object even though it increases the distance needed to move it.