# A rocket is launched vertically upward from the ground. Initially, the thrust force from the rocket engines is greater than the weight of the rocket. As the rocket rises, its engines continue to provide the same thrust force, but the rocket accelerates more and more quickly. Explain why the rocket accelerates, and why the acceleration increases as the rocket rises.

> WJEC A-Level Physics (Wales) — 1.2 Forces and Newton's laws · Explain · 5 marks

> A rocket burns fuel to produce a large downward thrust. As it rises through the atmosphere, air resistance is small enough to be ignored.

## Mark scheme (5 marks)

1. The thrust force is greater than the weight / there is a resultant (net) upward force
2. A resultant force causes acceleration (Newton's Second Law / F = ma)
3. As fuel is burned, the mass of the rocket decreases
4. For the same (constant) thrust force, a smaller mass produces a greater acceleration
5. The resultant force also increases (as weight decreases with decreasing mass), further increasing acceleration

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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-rocket-is-launched-vertically-upward-3a74e8a0) · Published by Druglandscape Ltd.