# A football is kicked and travels across a grass pitch before coming to a stop. Explain, using Newton's laws of motion, why the football eventually stops, and describe what would happen to the football's momentum as it slows down.

> OCR A-Level Physics B: Advancing Physics (H557) — 3.5 Newton's laws and momentum · Explain · 5 marks

> A footballer kicks a stationary ball. The ball rolls along the grass and gradually slows down before stopping completely.

## Mark scheme (5 marks)

1. A resultant (unbalanced) force acts on the football as it rolls
2. Friction (from the grass) acts in the opposite direction to the ball's motion
3. Newton's first law: an object will remain in motion unless acted upon by a resultant force — the friction provides this resultant force and causes the ball to decelerate
4. Newton's second law: the resultant force causes a change in momentum / the ball decelerates (its velocity decreases)
5. The momentum of the ball decreases (as velocity decreases) until it reaches zero when the ball stops

## Key terms

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

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](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-football-is-kicked-and-travels-5b6c6fe6) · Published by Druglandscape Ltd.