# Explain what is meant by the limit of proportionality and describe how the extension of a steel spring changes as increasing loads are applied, both before and after this limit is reached.

> AQA A-Level Physics (7408) — 3.4.2 Materials · Explain · 5 marks

## Mark scheme (5 marks)

1. The limit of proportionality is the point beyond which extension is no longer proportional to force/load
2. Before the limit of proportionality, extension is directly proportional to the force applied (Hooke's law is obeyed)
3. A graph of force against extension would be a straight line through the origin before the limit of proportionality
4. After the limit of proportionality, extension increases more rapidly / disproportionately for the same increase in force
5. After the limit of proportionality the spring may not return to its original length / may be permanently deformed when the load is removed

## Key terms

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

## 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/explain-what-is-meant-by-the-fdfb4b9e) · Published by Druglandscape Ltd.