University of Virginia
Physics Department

## Newton's 2nd Law of Motion

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.10

Objectives

Students will

• Understand how motion or distance traveled depends on mass and force.
• Investigate the relationship between force, mass, and acceleration as described by Newton’s 2nd Law of Motion.

Motivation for Learning

Driving Question

Propel an empty cart into a can using a rubber band for propulsion, and measure how far the can recoils. Add a 100 gram mass to the cart and repeat the experiment.

Materials

• Cart
• Large rubber band
• Tin can
• Meter stick
• 100 gram mass
• Tape

Procedure

1. Mark a starting point for the cart on the floor
2. Mark a point to which the rubber band should be pulled back, in order to have the same force applied each time.
3. Mark a starting point on the floor for the can.
4. Hold the two ends of the rubber band and pull it back to the designated mark.
5. Place the cart in front of the rubber band and pull it back to the designated mark.
6. Release the cart so it will hit the can.
7. Measure how far the can traveled.
8. Repeat after adding the 100 g mass to the cart. Attach the mass with tape.

Background Information

This experiment is designed to verify Newton’s 2nd Law of Motion. Force equals mass multiplied by acceleration. This law states that a force on an object will cause it to accelerate in the direction of the force. The greater the force exerted on the object, the greater the acceleration. For any given force, the greater the mass of an object, the smaller the acceleration.

In this experiment, the force will be applied by rolling balls of different masses down a ramp. A wooden, glass, and metal ball will be used to vary the force used. A small box (or paper cup) with a hole cut in one side will be used to measure the acceleration by measuring how far the box travels. The box will be placed at the bottom of the ramp to catch the balls. A second part of this experiment will use a constant force (metal ball), and the mass of the object at rest (the box) will be varied by adding washers to the top of the box.

The greater the mass of the ball rolling down the ramp, the farther the box should travel. When more mass (washers) is taped to the box, the box should move less.

### Student Activity

To print out the Student Copy only, click here.

Materials

• Ramp (1 meter long), can use cove molding or meter sticks with side rails on each side to keep the balls on the ramp;
• 3 balls, wooden, glass, and metal (12 mm or ½ inch works well);
• A small cardboard bow (7 x 6 x 4 cm), or a paper cup (cut a 3 x 3 hole in one side of the cup at the very top on one side);
• 3 medium size washers
• Meter stick
• 4 textbooks
• Tape
• Graph paper

Procedure

Part 1:

1. After reading the procedure, answer the 1st question before starting the experiment.
2. Make an inclined plane using the cove molding and four textbooks.
3. Place the box or cup upside down on the table at the bottom of the ramp with the opening facing the ramp, so it will catch a ball as it is rolled down the ramp.
4. Roll the wooden ball down the ramp and measure how far the box or cup moved from its starting position.
5. Record your data and repeat twice.
6. Roll the glass ball down the ramp and measure how far the box or cup moved from its starting position.
7. Record your data and repeat twice.
8. Roll the metal ball down the ramp and measure how far the box or cup moved from its starting position.
9. Plot your results, with the type of ball on the x-axis, and the distance the box or cup moved on the y-axis.

Part 2:

1. Tape 1 washer on top of the box or cup.
2. Roll the metal ball down the same ramp and measure how far the box or cup moved from its starting position.
3. Record your data and repeat twice.
4. Repeat with two washers, then with three washers.
5. Record your data and repeat twice.
6. Plot your results, with the number of washer on the x-axis, and the distance the box or cup moved on the y-axis.

Data Table

To print out Data Table only, click here.

Distance Traveled by the Cup (cm)

 Trial 1 Trial 2 Trial 3 Average Wooden Ball Glass Ball Metal Ball 1 Washer 2 Washers 3 Washers

Students with Special Needs

All students should be able to participate in this activity.

Click here for further information on laboratories with students with special needs.

Assessment

To print out the Data Table only, click here.

1. Write a hypothesis for both parts of this experiment.

2. How does the force of the moving object (type of ball) affect the distance traveled by the cup?

3. How does the mass of the object at rest (box or cup) affect how far it travels when hit by the metal ball?

4. Describe the relationship between force (mass of ball) and the distance the box or cup moved. Describe the relationship
between the mass of the box or cup, and the distance the box or cup moved. Do you agree with Newton’s 2nd Law of Motion?

5. Did your results support your hypothesis? Explain.