|
Review the
background information
for this lesson, especially the information
on pressure changes with temperature. You may also want
to review the information in the textbook on
gas laws
. Based on what you've learned, do you think a warm tennis ball
will bounce higher or lower than a tennis ball at room temperature?
|
|
Use new balls if possible. If you use old or
used tennis balls in this experiment be consistent - use
balls opened at the same time; used balls should
have the same amount of wear.
|
|
Determine the surface you will use. The International Tennis
Federation conducts ball bounce tests on concrete. You will
want to use a court or other (preferably hard)
surface. Since you will drop the ball straight down
and take measurements as the ball rebounds straight up, avoid windy areas.
|
|
To measure the drop and bounce height use a long tape
measure at least 100" long. Someone can hold
the tape measure up by carefully standing on a sturdy
chair or foot ladder or you can tape it to a fence or backboard.
|
|
Prepare the tennis balls.
Heat three of the balls. To heat:
- Balls can be left out in the sun for 2 hours or;
- Balls can be left out in the sun in a closed box for 1-2 hours or;
- Balls can be placed near or on a
safe heat source - wrapping the tennis balls in a heating pad works well.
Chill three of the balls. To chill:
- Place the balls in sealable plastic bags to prevent wetness.
- Place in a refrigerator or in a small ice chest with ice.
Room or outside temperature: Leave 3 balls out at room
temperature for 1-2 hours.
|
|
|
|
Measuring the temperature: there are several options to measure the temperature:
- Measure the temperature of the surrounding air with a thermometer;
- Use a thermometer to measure the temperature of the ball directly
- Determine ball warmth or coldness by touch.
Do not remove the heated or cold balls from their surroundings
until you are ready to test them.
|
|
Stand on a chair or footstool near the tape measure.
Hold a ball near the 100" mark of the
tape measure. Hold a ball with your fingertips and
drop the ball. Let the ball fall straight down
- don't push it. How high does the ball
bounce on the rebound? Record the height on your
chart. Repeat this procedure for each ball until you have
at least 10 data points for each range of ball temperatures.
Optional - You can set a video camera up to record
the bounce height. Keep the camera focused in the
52" range on the tape measure. You will
probably have to adjust the camera height when you test
different ball temperatures.
|
|
Average your data for each ball temperature: add the 10
ball heights together and then divide by 10.
Record the range of heights for each ball temperature.
Plot the temperatures and heights. Use a different color in
the plot for each temperature range
Which bounces higher? Why do you think it bounces higher?
|
|
Variations: You can try this experiment with different brands
of balls, balls meant for different courts, old
balls, worn balls. Does your data look different?
|
|
