# A spacecraft travels from Earth to Mars. During the journey, the spacecraft moves away from Earth and closer to Mars. Explain how the weight of the spacecraft changes during this journey, and why its mass remains the same throughout.

> OCR A-Level Physics A (H556) — 2.1 Physical quantities and units · Explain · 5 marks

> Earth has a much stronger gravitational field than Mars. In deep space, far from any planet, the gravitational field strength is approximately zero.

## Mark scheme (5 marks)

1. Weight depends on gravitational field strength (not mass alone)
2. As the spacecraft moves away from Earth, the gravitational field strength decreases, so the spacecraft's weight decreases
3. In deep space (far from any planet) the gravitational field strength is approximately zero, so the weight of the spacecraft is approximately zero
4. As the spacecraft approaches Mars, gravitational field strength increases, so its weight increases again
5. Mass remains the same because mass is the amount of matter in the spacecraft and does not depend on gravitational field strength / location

## Key terms

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

## Related

- [Revision notes for OCR A-Level Physics A (H556)](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/a-spacecraft-travels-from-earth-to-a0700179) · Published by Druglandscape Ltd.