# A car is travelling along a straight road at a constant speed of 20 m/s. The driver then applies the brakes and the car slows down to a stop. Explain the difference between speed and velocity, and explain what is meant by the car having a negative acceleration as it slows down.

> Eduqas GCSE Physics — 4.1 Speed, velocity and acceleration · Explain · 4 marks

## Mark scheme (4 marks)

1. Speed is a scalar quantity — it has magnitude only / only tells you how fast an object is moving
2. Velocity is a vector quantity — it has both magnitude and direction / velocity is speed in a stated direction
3. Acceleration is the rate of change of velocity
4. Negative acceleration (deceleration) means the velocity is decreasing / the car is slowing down so the change in velocity is in the opposite direction to motion

## Key terms

- [speed](https://www.gradenine.co.uk/glossary/speed)
- [velocity](https://www.gradenine.co.uk/glossary/velocity)
- [acceleration](https://www.gradenine.co.uk/glossary/acceleration)

## Related

- [Revision notes for Eduqas GCSE 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-along-a-44dfcf81) · Published by Druglandscape Ltd.