# A car is travelling at high speed when the driver suddenly sees a hazard ahead. The car has a seat belt fitted as a safety feature. Explain why wearing a seat belt reduces the risk of serious injury to the driver during the collision that follows.

> Eduqas A-Level Physics — 4.2 Kinetic theory and gases (A-Level only) · Explain · 5 marks

> A driver is travelling along a motorway at high speed. The driver notices a hazard and reacts, but the car collides with the hazard before it can stop.

## Mark scheme (5 marks)

1. The driver has momentum (due to their mass and velocity) before the collision
2. During the collision the driver's momentum must change (to zero / decreases to zero)
3. The seat belt increases the time over which the momentum change occurs
4. Force is equal to the rate of change of momentum, so a longer time means a smaller force
5. Therefore the force experienced by the driver is reduced, lowering the risk of injury

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](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-car-is-travelling-at-high-5092ce7b) · Published by Druglandscape Ltd.