Q1.
Take each ball and drop it from a fixed height. Note the height to which the ball bounces and record it in Table 6.2. Identify the ball that achieves the highest bounce.
Answer
Method: stand each ball beside a wall, mark a fixed height (say 1 m) with chalk, drop the ball from that mark without throwing it down, and have a friend note how high it returns. Repeat three times for each ball and take the best reading. Use the same height and the same floor every time, otherwise the comparison is unfair.
| Table 6.2: Bouncing level of the balls | ||
|---|---|---|
| Ball | Bounce (high, medium or low) | Reason — the material |
| Tennis ball | High | Hollow rubber filled with air — squashes on landing and springs back fully |
| Cricket ball | Low | Cork wound with thread inside a leather cover — hard, hardly changes shape |
| Hand exercise ball | Medium | Solid soft rubber — it squashes, but a lot of the energy is used up inside |
| Any other — rubber ball | High | Solid rubber, very springy |
| Any other — plastic (hollow) ball | Medium | Thin plastic, light; bounces but not as much as rubber |
| Any other — clay ball | None (it breaks) | Baked clay is hard but brittle |
Ball with the highest bounce: the tennis ball.
Why it happens: all three balls are of the same size, so the only difference is the material. Rubber is elastic — it changes shape when it hits the floor and then pushes itself back, returning almost all the energy. Cork-and-leather and baked clay do not spring back, so the energy is lost and the ball stays down.
Check it yourself: Repeat the same drop on sand or on a mattress. Even the tennis ball hardly bounces, because now the floor soaks up the energy. Bounce depends on both surfaces, not just the ball.