slug Created with Sketch. Science Questions

Why do balls bounce when they’re filled with air?

Let’s use the example of a beach ball. The air in it always pushes outward in all directions against the inside of the ball. When you drop the ball onto a hard floor, both the ball itself and the air inside it get flattened or squeezed a little by the impact. (The floor does, too!)

The squeezed air, under greater pressure, pushes out with greater force, returning the ball to its round shape. The rebounding ball “pushes off” the floor—which you see as a bounce.

Thinking Challenge

Which would be the better bouncer — a beach ball that is fully inflated or the same ball with less air in it? Why? Think of your best answer. Then read our explanation below.

Thinking Challenge Answer

The ball that’s fully inflated would bounce better. As a ball bounces, it squashes a little and then returns to its original shape. In the process, it heats up a little bit, losing a small amount of energy. When the ball is fully inflated, it squashes less than when it’s not as inflated, so it heats up less. With less energy lost to heat, it can bounce higher.

Photo by: iStock|lucato

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