STEM Activity: Bounce Into Tennis Science

Have you ever wondered why tennis players bounce the ball on the court before they serve? One reason for this practice is to help players focus their attention on the game, but they are also testing the bounce of the ball. Tennis matches are played on different courts — hard courts, clay courts and sometimes even on grass. Since a tennis ball doesn’t bounce the same way on each surface, bouncing the ball gives a tennis player important data for their game!

Ready to ace your next STEM experiment? Grab a tennis ball to explore how different surfaces affect the object’s bounce and motion, and how these differences shape the way tennis is played!

Materials Needed

• Clay or dirt surface
• Grass surface
• Hard surface (sidewalk or gym floor)
• Measuring tape or ruler
• Paper
• Pencil
• Tennis ball

Step-by-Step Instructions

1. Choose a safe location where you can test three different surfaces: a hard surface, a clay or dirt surface, and a grassy area.
    
2. Hold the tennis ball above your head and drop it. To make your bounce easier to observe, try dropping it from a safe, sturdy, higher location.
    
3. Drop the ball onto the hard surface and watch how high it bounces.
    
4. Have a partner measure the height of the bounce. You can use a ruler, measuring tape or a nonstandard unit of measurement, like your height or a broomstick. Record the bounce height on your paper.
    
5. Repeat the drop one more time on the same surface and record your results. How does your second drop compare to the first drop?
    
6. Repeat steps two through five on the clay or dirt, and on the grass surface.
   
   Have fun making predictions about the height of the bounce on each surface.
    
7. Compare the heights of all the bounces to determine which surface caused the ball to bounce the highest and the lowest.
    
8. Share your discoveries with a friend or family member. For an additional challenge, consider testing other types of balls too!

What Are We Discovering?

As you experimented with different surfaces, you were uncovering the physics behind tennis! When you drop a tennis ball, gravity pulls it down toward the ground. When the ball hits the surface, it pushes upward on the ball with force. This force causes the ball to slow down and change direction, bouncing upward. How high the ball bounces depends, in part, on how much force the surface applies to change the ball’s motion when it bounces.

You might have noticed how soft surfaces resulted in a lower bounce. Soft surfaces absorb more energy, meaning less energy returns to the ball. Because hard surfaces don’t absorb as much energy, much more energy returns to the ball, causing it to bounce higher. Think about your results: On which surface would you rather play tennis and why? Would you want the ball to bounce high or stay low?

The way surfaces affect a bouncing tennis ball can change how players interact with it during a game. Some scientists and inventors also like to study how forces like this can be controlled. National Inventors Hall of Fame^® Inductee Howard Head designed a tennis racket with a wider frame made of aluminum. The new design increased the size of the racket’s sweet spot, the best place to make contact with the ball, and made shot-making easier and more effective for players.

Stay in The Game

Want to find more ways STEM powers your favorite games? Check out this activity to discover more about forces and motion, and find more ideas for STEM exploration on our blog.