Name: _________________
Making the Grade
Period: _________________
Partners: _________________
One of the simplest machines that makes doing work easier is the inclined
plane, or ramp. It is much easier to push a heavier load up a ramp than it is to lift the
same amount straight up.
Let's begin with the picture on the right. A hill has three paths up its sides to a flat
summit area. The three path lengths are different, but the vertical height from the
bottom of the mountain to the top is the same.
1)
Which path would be easiest for a car to climb? Explain your answer.
2)
Not including the energy used to overcome the internal friction of the car, which path requires the most energy
(gasoline) for a car to climb? Explain your answer.
Procedure:
Record the mass of your cart + 1kg mass: ____________
Place a crossbar on a ring stand. Record the height of the crossbar: ________
Place the board at an angle, as shown in the diagram. Pull the cart (with a 1kg mass)
up the ramp with a spring scale kept parallel to the board to measure the force. Stop
the cart when the back end has passed point where the crossbar is touching the board.
Measure the displacement that the cart travels (s). In this lab you will get the best
data if you measure the displacement from the bottom of the ramp to the crossbar. Be
sure the back of the cart passes the finish line. Record all values in the chart below.
Move the board so that it is at a new angle--do not move the crossbar. Repeat the procedure from above for at least 6
angles between about 10° and 60°. Each time pull the cart up to the same height.
Approximate angle
10°
60°
Force (N)
Displacement (m)
Height (m)
3)
What is the relationship between the force and displacement? If force goes up, what happens to the amount of
displacement?
Work is loosely defined as the amount of energy expended on an object. You do this by exerting a force on the object,
and your energy is transferred to that object. We will talk more about this later, though. Work is done when you exert a
force for a certain displacement. If the object doesn't go anywhere, you don't do ANY work on the object! The object is
getting NONE of your energy! Work is the amount of energy transferred. If you remember from Chemistry, energy
was measured in Joules.
Work is calculated by the following formula:
Work = Force * Displacement
Calculate the work done on the cart for each trial. Show one sample calculation below:
Approximate angle
10°
60°
Work (J)
4)
You made BIG changes in the angle of your incline. Are there BIG changes in the amount of work done?
Now, based on what you've learned in this lab, re-answer the first two questions with reasoning based on the lab.
1)
2)
5)
Now it’s time to make a prediction using the data in section 3. If you lifted the cart+mass straight up to the height of
the crossbar, not using the ramp, calculate how much work would you expect to do. (Hint: think average)
Using this amount of work, along with the height of the crossbar, how much force will you have to use to lift the
cart+mass straight up?
Now hang the cart+mass from the scale and record the actual force required. Write the measured force here, and
calculate your % difference between the calculated force and the measured force.
Measured Force: _______
% Difference =
| Measured – Calculated |
(Average of Measured and Calculated)
X 100