# Explain why a planet in a circular orbit around the Sun remains at a constant distance from the Sun, even though a gravitational force acts on it.

> Eduqas GCSE Physics — 10.1 Solar system; stability of orbital motions; satellites · Explain · 4 marks

## Mark scheme (4 marks)

1. Gravity acts as a centripetal force on the planet
2. The gravitational force changes the direction of the planet's velocity / acts at right angles to the velocity
3. The planet moves in a curved / circular path around the Sun
4. The distance from the Sun stays constant because the planet's speed (magnitude of velocity) remains unchanged

## Key terms

- [gravitational force](https://www.gradenine.co.uk/glossary/gravitational-force)
- [circular orbit](https://www.gradenine.co.uk/glossary/circular-orbit)

## 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/explain-why-a-planet-in-a-21259a05) · Published by Druglandscape Ltd.