# A car travels along a straight road. It starts from rest and accelerates uniformly for 8 seconds, reaching a speed of 20 m/s. It then travels at a constant speed of 20 m/s for 12 seconds. Finally, the driver applies the brakes and the car decelerates uniformly to rest in 4 seconds. Describe the motion of the car during each of the three stages and explain what the velocity–time graph for the entire journey would look like.

> Edexcel A-Level Physics (9PH0) — 2.1 Motion · Describe · 5 marks

> A car travels along a straight road. It starts from rest and accelerates uniformly for 8 seconds, reaching a speed of 20 m/s. It then travels at a constant speed of 20 m/s for 12 seconds. Finally, the driver applies the brakes and the car decelerates uniformly to rest in 4 seconds.

## Mark scheme (5 marks)

1. Stage 1: the car accelerates uniformly / the velocity increases at a constant rate from 0 to 20 m/s
2. Stage 1 on the graph: a straight line with a positive gradient (sloping upward) from the origin
3. Stage 2: the car travels at constant velocity / no acceleration / resultant force is zero
4. Stage 2 on the graph: a horizontal straight line at 20 m/s
5. Stage 3: the car decelerates uniformly / velocity decreases at a constant rate back to zero, shown as a straight line with a negative gradient ending at zero velocity

## Key terms

- [velocity–time graph](https://www.gradenine.co.uk/glossary/velocity-time-graph)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-travels-along-a-straight-dc7f8d9a) · Published by Druglandscape Ltd.