You already know that the force of gravity is what causes a ball to drop to the ground -- but did you know that same force can give the ball a high bounce? That's because the force of gravity can be converted to energy.
When a ball strikes the ground, the downward force from gravity is converted into upward force, which then works against gravity to send the ball up in the air.
As you'll see, different materials and sizes of the balls affect how well each one converts the energy into upward force -- and that affects how high each ball will bounce.
What You'll Need:
- Balls of various sizes and materials
- Graph paper
- Large sheet of cardboard
- Tape measure
Step 1: Collect some different balls, such as a tennis ball, beach ball, softball, rubber ball, football, basketball, and golf ball.
Step 2: Make a graph that lists the names of the different balls across the bottom and that lists the height in feet along the sides.
Step 3: Test the different balls to see which one bounces best on a concrete floor, porch, or driveway.
Step 4: Set the cardboard sheet against a wall, or ask two friends to hold it upright. Then drop the balls, one at a time, from the same height, in front the sheet of cardboard.
Step 5: Mark on the cardboard how high each one bounced.
Step 6: Measure each bounce, and indicate it on your graph.
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ABOUT THE CONTRIBUTING WRITER:
Spit Don't Quit by Peter Rillero, Ph.D.
Peter Rillero, Ph.D. is the Department Chair of Secondary Education and associate professor of science education at Arizona State University in Phoenix. He is the author of Time for Learning: Science; Time for Learning: The Human Body, and Totally Creepy Bugs and the co-author of the best-selling high school biology textbook in the United States. Rillero has conducted two program evaluations of the world's largest science fair, the Intel International Science and Engineering Fair. His Web site is: www.west.asu.edu/rillero
Computer Illustration by: Rémy Simard