# A driver is travelling along a motorway at a constant velocity when they suddenly see an obstacle on the road ahead. Explain why the total stopping distance of the vehicle depends on both the driver and the condition of the vehicle and road.

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

> A driver travelling at constant velocity on a motorway must stop suddenly to avoid an obstacle.

## Mark scheme (5 marks)

1. Thinking distance depends on the driver's reaction time
2. Reaction time (and therefore thinking distance) can be increased by tiredness, drugs or alcohol
3. Braking distance is the distance travelled under the braking force after the brakes are applied
4. Adverse road or weather conditions increase braking distance
5. Stopping distance is the sum of thinking distance and braking distance

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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-driver-is-travelling-along-a-bb8a52c0) · Published by Druglandscape Ltd.