Lab #9 - Coefficient of Restitution
Purpose:
The purpose of this lab is to explore the variation in the coefficient of restitution (e) in different situations; and to
investigate the variables (factors) influencing the bouncing of balls.
Equipment
Basketballs
Golf balls
Tennis balls
Tape measure
Masking tape
Ruler
General procedures
1.
Attach a tape measure to the wall in a location where you have enough room to complete the experiment.
2.
Drop all balls from the same height. Line the ball up so the top of the ball is always at the same height
(use tape measure perpendicular to the wall to line this up). Be careful not to give upward or downward
velocity to the ball when dropping it.
3.
Measure all bounce heights to the TOP of the ball. You will have to make a trial drop to see the
approximate rebound height so the person who will read the result will be able to get lined up in the right
spot to get as accurate a reading as possible. Read results to the nearest half- inch.
4.
Use the mean of 5 trials for each situation.
5.
Use the following formula to calculate the coefficient or restitution for all situations.
e=
6.
rebound ht
drop ht
Record all results and values on the attached data sheet.
Experiment 1: Temperature variation
Tennis balls and golf balls have been preheated and pre-chilled for use in this experiment.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Obtain a chilled tennis ball from the ice bucket.
Make one trial drop to determine the approximate height to line up at to accurately read the results.
Conduct 5 drops.
Return the tennis ball to the ice bucket.
Repeat #1-4 with a chilled golf ball.
Obtain a heated tennis ball. Be sure to keep the tennis ball warm as you transport it.
Repeat steps 2 and 3 above. Return the tennis ball to the hot pack.
Repeat steps 6-7 with a heated golf ball.
Obtain a tennis ball that has been kept at room temperature.
Repeat steps 2 and 3 above.
Obtain a golf ball that has been kept at room temperature.
Repeat steps 2 and 3 above.
Experiment #2: Inflation pressure
Basketballs have been prepared at three different inflation levels – full, -1 lb, -2 lbs. these are marked as such.
Be sure to obtain one of each for this experiment.
1.
2.
3.
4.
5.
Obtain the three basketballs.
Take the fully inflated ball. Make one trial drop to determine the approximate height to line up to
accurately read the results.
Conduct 5 drops.
Repeat steps 2 and 3 for each of the two other inflation levels.
Return the basketballs.
Experiment #3: Different surfaces
Obtain a normal basketball, normal tennis ball, normal golf ball, a carpet square, and some masking tape.
1.
2.
3.
4.
5.
Using the tile floor of the lab: make one drop to determine the approximate height to line up at to
accurately read the results.
Conduct 5 drops.
Repeat steps 1 and 2 while dropping the ball on the carpet square.
Go to the wood floor in the gym. Tape the tape measure to the wall and repeat steps 1 and 2 on the wood
floor.
Go out the back door of the lab and use the asphalt surface behind the building. Tape the tape measure to
the side of the building and repeat steps 1 and 2.
Results:
Experiment 1: Temperature
Drop height: _________________
Trail 1
Trail 2
Trail 3
Trail 4
Trail 5
Mean
e
Trail 2
Trail 3
Trail 4
Trail 5
Mean
e
Chilled tennis ball
Heated tennis ball
Room temp. tennis ball
Chilled golf ball
Heated golf ball
Room temp. golf ball
Experiment 2: Inflation pressure
Drop height: ________________
Trail
1
Full
- 1 lb
- 2 lbs
Experiment 3: Different surfaces
Drop height: __________________
Trial 1
Trial 2
Ball: ____________________
Trial 3
Trial 4
Trial 5
Mean
e
Tile
Carpet
Wood
Asphalt
Drop height: __________________
Trial 1
Trial 2
Ball: ____________________
Trial 3
Trial 4
Trial 5
Mean
e
Tile
Carpet
Wood
Asphalt
Drop height: __________________
Trial 1
Trial 2
Ball: ____________________
Trial 3
Trial 4
Trial 5
Mean
e
Tile
Carpet
Wood
Asphalt
Coefficient of restitution questions:
1. What is the possible range in the values for the coefficient of restitution?
2. How does changing the temperature influence the value of the coefficient of restitution?
3. How does temperature influence the bounce of a ball?
4. Describe two sport situations where temperature may influence the coefficient of restitution in a
game?