# A spacecraft is travelling through deep space, far from any planet or star, with its engines switched off. A student claims that the spacecraft will gradually slow down and eventually stop. Explain why the student is wrong, using Newton's First Law in your answer.

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

> A spacecraft is moving through deep space at a constant speed of 3000 m/s. Its engines are switched off and there are no significant gravitational forces acting on it.

## Mark scheme (4 marks)

1. Newton's First Law states that an object continues at constant velocity if the resultant force acting on it is zero
2. In deep space there is no air resistance (or friction / resistive force) acting on the spacecraft
3. The resultant force on the spacecraft is therefore zero
4. Therefore the spacecraft continues to move at a constant velocity and will not slow down

## Key terms

- [Newton's First Law](https://www.gradenine.co.uk/glossary/newton-s-first-law)

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-spacecraft-is-travelling-through-deep-107e4fca) · Published by Druglandscape Ltd.