# A buoy floating on the sea bobs up and down in simple harmonic motion. Explain what is meant by simple harmonic motion and describe the resultant force and acceleration acting on the buoy at different positions during one complete oscillation.

> AQA A-Level Physics (7408) — 3.6.1 Periodic Motion · Explain · 5 marks

> A buoy is anchored to the seabed. Ocean waves cause the buoy to oscillate vertically about its equilibrium position.

## Mark scheme (5 marks)

1. The resultant force (and acceleration) always acts towards the equilibrium position
2. The magnitude of the resultant force (and acceleration) is proportional to the displacement from the equilibrium position
3. At the equilibrium position the resultant force is zero and the acceleration is zero
4. At maximum displacement (amplitude) the resultant force and acceleration are at their maximum values
5. As the buoy moves from maximum displacement back to equilibrium, the force and acceleration decrease; as it moves from equilibrium to the opposite maximum, the force and acceleration increase in the opposite direction

## Key terms

- [simple harmonic motion](https://www.gradenine.co.uk/glossary/simple-harmonic-motion)

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-buoy-floating-on-the-sea-30b69939) · Published by Druglandscape Ltd.