# A cyclist rides along a flat road. The cyclist's legs exert a force to turn the pedals, but the bicycle does not travel as far as it would if all the input energy were converted into kinetic energy. Explain why the bicycle has an efficiency of less than 100% and describe TWO ways in which the efficiency of the bicycle could be increased.

> OCR GCSE Physics A: Gateway Science (J249) — P5.2 Power and efficiency · Explain · 4 marks

> A cyclist notices that, over time, the chain on their bicycle becomes dry and the wheel bearings feel stiff. They want to improve how efficiently the bicycle transfers energy.

## Mark scheme (4 marks)

1. Some input energy is transferred as waste energy (e.g. heat due to friction between moving parts / sound), rather than as useful kinetic energy
2. Because energy can never be created or destroyed (conservation of energy), the useful output energy can never exceed the total input energy, so efficiency is always less than or equal to 1 (100%)
3. Applying lubrication (e.g. oiling the chain/bearings) reduces friction between moving parts, reducing the waste energy transfer as heat
4. A second valid method of increasing efficiency, e.g. using thermal insulation to prevent heat dissipating to the surroundings / recycling waste energy so it can be reused

## Key terms

- [efficiency](https://www.gradenine.co.uk/glossary/efficiency)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](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-cyclist-rides-along-a-flat-78255afe) · Published by Druglandscape Ltd.