# A comet travels in an elliptical orbit around the Sun. As the comet moves closer to the Sun, its orbital speed increases. Explain why the comet speeds up as it approaches the Sun, and state what happens to the direction of the comet's velocity during this part of its orbit.

> Pearson Edexcel International GCSE Physics (4PH1) — 1.4 Astronomy · Explain · 4 marks

> Comets travel in highly elliptical orbits. At its closest point to the Sun, a comet may be travelling many times faster than at its most distant point.

## Mark scheme (4 marks)

1. Gravity (gravitational force) acts on the comet towards the Sun
2. This resultant force causes the comet to accelerate (Newton's second law)
3. Acceleration means the comet's speed increases (as it moves towards the Sun)
4. The direction of the comet's velocity continuously changes as it follows the curved elliptical path

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-comet-travels-in-an-elliptical-d4afda9e) · Published by Druglandscape Ltd.