# A steel spring is stretched by hanging weights from it. At first, the extension increases in proportion to the load. When a very heavy load is applied, the spring does not return to its original length after the load is removed. Explain what happens to the spring at each stage, using the terms limit of proportionality, elastic deformation, and plastic deformation in your answer.

> Pearson Edexcel International GCSE Physics (4PH1) — 1.3 Forces, movement, shape and momentum · Explain · 4 marks

> A steel spring is hung vertically and weights are added one at a time. For small loads, each equal increase in load produces the same increase in extension. Beyond a certain point, equal increases in load produce larger and larger increases in extension, and the spring is permanently stretched.

## Mark scheme (4 marks)

1. For small loads, the spring undergoes elastic deformation
2. Up to the limit of proportionality, extension is directly proportional to the load / Hooke's law is obeyed
3. Beyond the limit of proportionality, extension is no longer directly proportional to the load
4. When the very heavy load is applied and removed, the spring has undergone plastic deformation, so it does not return to its original shape / length

## Key terms

- [limit of proportionality](https://www.gradenine.co.uk/glossary/limit-of-proportionality)
- [elastic deformation](https://www.gradenine.co.uk/glossary/elastic-deformation)
- [plastic deformation](https://www.gradenine.co.uk/glossary/plastic-deformation)
- [extension](https://www.gradenine.co.uk/glossary/extension)

## 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-steel-spring-is-stretched-by-0806c593) · Published by Druglandscape Ltd.