# Explain why a satellite in a circular orbit at a greater distance from Earth's centre moves with a smaller orbital speed than a satellite in a circular orbit at a smaller distance.

> IB DP Physics Standard Level (2023 syllabus) — D.1 Gravitational fields · Explain · 4 marks

## Mark scheme (4 marks)

1. Gravitational force provides the centripetal force for circular orbital motion
2. Gravitational field strength / gravitational force decreases with increasing distance from Earth's centre (inverse-square relationship)
3. For a circular orbit, the centripetal acceleration (or force) required is proportional to v²/r, so a smaller force at larger r requires a smaller value of v²/r
4. Therefore, the satellite at greater orbital radius requires a smaller speed to maintain a stable circular orbit

## Key terms

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

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](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-satellite-in-a-7cc60ebd) · Published by Druglandscape Ltd.