# A rubber bungee cord is stretched by a person jumping from a bridge. At first, the cord extends in proportion to the force applied to it. As the jump continues, the cord is stretched further until it no longer obeys Hooke's law. Explain the behaviour of the bungee cord during the jump, referring to the limit of proportionality and elastic deformation.

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

> A bungee cord has a spring constant of 50 N/m. During a jump, the cord is first stretched gently, then stretched to a much greater extension as the jumper falls.

## Mark scheme (4 marks)

1. Initially, the extension of the cord is directly proportional to the force applied (Hooke's law is obeyed).
2. Beyond the limit of proportionality, the extension is no longer directly proportional to the force applied.
3. As long as the elastic limit is not exceeded, the cord undergoes elastic deformation and returns to its original shape/length when the force is removed.
4. If the elastic limit is exceeded, plastic (permanent) deformation occurs and the cord will not return to its original shape.

## Key terms

- [limit of proportionality](https://www.gradenine.co.uk/glossary/limit-of-proportionality)
- [elastic deformation](https://www.gradenine.co.uk/glossary/elastic-deformation)
- [Hooke's law](https://www.gradenine.co.uk/glossary/hooke-s-law)

## 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-rubber-bungee-cord-is-stretched-d9f1a4b5) · Published by Druglandscape Ltd.