University of Virginia
Physics Department

## Newton's Second Law: F = ma

A Physical Science Activity

Student Activity

Materials

• Cart (20-25 cm long)
• 10-32 x 1 1/4 " bolt and nut
• 3 large rubber bands
• 500 g mass
• Ruler
• Meter stick
• Graph paper (8x11)

Procedure

1. Screw the bolt and nut through a hole at one end of the cart, so that the long end of the bolt forms a post at one end of the cart (see diagram below).
2. Place the cart on an open surface at least 5-6 m long (perhaps the floor). Mark its starting point on the surface with a piece of masking tape.
3. While one person holds the back of the cart, another should hook a rubber band around the front post.
4. Extend the rubber band about 35 cm in front of the car.
5. The person holding the back of the cart should let go, allowing the cart to roll forward.
6. Measure the distance the cart travels. Record this on the data table.
7. Replace the cart at its starting point. Repeat steps 2-5 with two rubber bands and then with three rubber bands.
8. Replace the cart at its starting point. Place the 500 g mass inside the cart.
9. Hold the cart, attach one rubber band and repeat steps 3-6. Repeat with two and three rubber bands.
10. Plot your data on a piece of graph paper. Label the y-axis (vertical) "Distance traveled" in units of meters. Label the x-axis (horizontal) "Force." The force unit will be the number of rubber bands attached to the cart. Draw two separate lines-one using the data from the empty carts, and another for the carts containing the 500 g mass.

Data Sheet

 Cart Type Distance Cart with one rubber band Cart with two rubber bands Cart with three rubber bands Cart with 500 g/ one rubber band Cart with 500 g/ two rubber bands Cart with 500 g/ three rubber bands

Questions

1. How is distance related to force in this experiment? To mass?

2. Describe the relationship between distance and acceleration. How would an increase or decrease in one value affect the other?

3. State Newton's Second Law in your own words. Do your results agree with this law? Why or why not?