# A tennis ball is travelling at high speed towards a wall. The ball collides with the wall and bounces back in the opposite direction at a lower speed. Explain why the ball experiences a change in momentum during this collision, and describe what happens to the magnitude of the ball's momentum.

> AQA GCSE Physics (8463) — 4.5.7 Momentum (Phys only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Momentum is the product of mass and velocity / momentum = mass × velocity
2. A force acts on the ball from the wall during the collision, causing a change in momentum
3. The ball's velocity changes direction (from towards the wall to away from the wall), so its momentum changes direction
4. The magnitude of the ball's momentum decreases because the ball bounces back at a lower speed than it arrived (with same mass)

## Key terms

- [momentum](https://www.gradenine.co.uk/glossary/momentum)
- [change in momentum](https://www.gradenine.co.uk/glossary/change-in-momentum)

## Related

- [Revision notes for AQA GCSE Physics (8463)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-tennis-ball-is-travelling-at-b12d9289) · Published by Druglandscape Ltd.