# A guitar string is plucked and vibrates in simple harmonic motion. Explain how the displacement, velocity, and acceleration of the string change as it moves from its maximum displacement back to its equilibrium (undisturbed) position, and state what happens to the amplitude of the vibrations over time if no further energy is supplied.

> WJEC A-Level Physics (Wales) — 5.1 Simple harmonic motion · Explain · 5 marks

> When a guitar string is plucked, it is displaced from its equilibrium position and then released, oscillating back and forth in simple harmonic motion.

## Mark scheme (5 marks)

1. At maximum displacement the velocity of the string is zero
2. As the string moves towards the equilibrium position, its velocity increases
3. The acceleration (restoring force) is greatest at maximum displacement and directed towards the equilibrium position
4. At the equilibrium position, velocity is at its maximum
5. Without an energy input, the amplitude decreases over time (the vibrations die away / the string loses energy to its surroundings)

## Key terms

- [amplitude](https://www.gradenine.co.uk/glossary/amplitude)
- [displacement](https://www.gradenine.co.uk/glossary/displacement)
- [simple harmonic motion](https://www.gradenine.co.uk/glossary/simple-harmonic-motion)
- [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-guitar-string-is-plucked-and-d7e86048) · Published by Druglandscape Ltd.