The lab below consists of three different stations.  I put out several setups of the two stations with the bouncy and non-bouncy balls.  The students complete this part of the experiment with a partner.  I stay with the tennis ball cannon station and monitor it closely. I get groups of about 6 students at a time to work with the cannon.  The bouncy and non-bouncy balls are sold in several different catalogs as “happy & unhappy balls” for around \$4 a pair. - Andy

Materials:

• Tennis Ball Cannon as described in The Dick and Rae Physics Demo Notebook on page M-562.
• TI-83 graphing calculator, CBL, and Vernier Photo gate
• Index card
• Balance

# HIGH SPEED PROJECTILE!

Procedure:

1. Tape an index card to the top of the cannon so it resembles a fin.
2. Set up the equipment as shown in the diagram.
3. The photo gate is arranged so the index card passes through the photo gate.
4. Ideally the card breaks the beam just as the ball exits the cannon. In reality, if the
5. cart’s friction is low the photo gate can be set back a bit.
6. Set up the photo gate system to record the time it takes the
7. index card to pass through the beam.
8. Put the tennis ball in the cannon
9. Prepare CBL system
10. put the flammable material in the cannon
11. make sure down range is clear
12. F I R E ! !

# Questions

1. By measuring the length of the index card you can calculate the speed of the cannon.Show your work!
2. Now you need the mass of the cannon and the ball.  You can then solve for the velocity of the ball using conservation of momentum. (Note: if Vcannon is + then Vball is - )

# Materials

• One bouncy & one non bouncy ball  & one ball of another material
• Meter stick

Procedure

1. Hold the meter stick with the 0 cm mark on the floor.
2. Hold a ball with the bottom of the ball even with the 100 cm mark.
3. Drop the ball and measure the height that it bounces back up off of the floor.
4. Repeat this 10 times and determine the average.
5. Calculate the coefficient of elasticity.
6. Repeat for the two other balls

# Questions

3. What would a 100% elastic ball do?  What would a 0% elastic ball do?

4. Under what conditions can you have 100% elastic collisions?

5. Is it possible to have 100% inelastic collisions? Give an example or two.

6. How does a physicist’s definition of elastic differ from the everyday use of the term?

Elastic and Inelastic collisions

• one bouncy & one non bouncy ball

• small wooden rectangular block

• section of hot wheels track

# Procedure

1. Set up the equipment as shown.
2. Allow the bouncy ball to roll  down the hill and strike the ball.  Measure how  far the block is shoved.Record your observations of what the ball and block do as they collide.
3. Repeat the experiment with the non bouncy ball.  Release it from the same height on the ramp. Measure how far the block is shoved.  Record your observations of what the ball and block do as they collide.

NOTE - Since these balls are released from the same height they will impact the block with the same speed.  The balls also have very nearly the same mass.

# Questions

7.  Which ball strikes the block with the greater force?  How do you know?

8. Which ball has the greatest impulse during collision? How do you know?

9. Identify each of the collisions as elastic or inelastic.

10. Draw a before and after picture for each collision. Write the equation showing conservation of momentum for each collision.