# A car travelling at high speed brakes suddenly and comes to a stop. Explain why a driver who is tired takes a longer stopping distance than a fully alert driver travelling at the same speed.

> Pearson Edexcel International GCSE Physics (4PH1) — 1.3 Forces, movement, shape and momentum · Explain · 4 marks

> Two drivers are travelling at the same speed along a straight, dry road in identical cars. Driver A is fully alert, whilst Driver B has not slept for 24 hours. Both drivers apply the brakes when they see the same hazard ahead.

## Mark scheme (4 marks)

1. Tiredness increases the driver's reaction time
2. A longer reaction time means the vehicle travels further before the brakes are applied, increasing the thinking distance
3. The braking distance is the same for both drivers (road and car conditions are identical and speed is the same)
4. Stopping distance is the sum of thinking distance and braking distance, so the greater thinking distance means a longer overall stopping distance for the tired driver

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](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-travelling-at-high-speed-437629a7) · Published by Druglandscape Ltd.