# A car travels at a constant speed around a circular roundabout. Explain why a net force must act on the car even though its speed does not change, and describe the direction of this force.

> WJEC A-Level Physics (Wales) — 1.5 Circular motion (A-Level only) · Explain · 5 marks

> A car enters a roundabout and maintains a constant speed as it travels in a circular path around the central island.

## Mark scheme (5 marks)

1. Velocity is a vector quantity that includes direction (not just speed)
2. The direction of motion continuously changes as the car travels in a circle
3. A change in direction means a change in velocity, which means the car is accelerating
4. A net (resultant) force is needed to produce an acceleration / to cause a change in velocity
5. The net force acts towards the centre of the circular path (centripetal direction)

## Key terms

- [net force](https://www.gradenine.co.uk/glossary/net-force)

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-car-travels-at-a-constant-0d5d02e7) · Published by Druglandscape Ltd.