# A petrol-powered go-kart engine transfers 12 000 J of chemical energy every second. Only 3 600 J per second is transferred as useful kinetic energy to move the kart forward. Explain why the go-kart engine cannot be 100% efficient, and describe what happens to the energy that is not usefully transferred.

> Edexcel A-Level Physics (9PH0) — 8.1 Particle accelerators and detectors · Explain · 5 marks

> A petrol-powered go-kart engine transfers 12 000 J of chemical energy every second. Only 3 600 J per second is transferred as useful kinetic energy to move the kart forward.

## Mark scheme (5 marks)

1. Energy cannot be created or destroyed (conservation of energy) so all input energy must be accounted for
2. Some energy is dissipated / transferred to the surroundings as heat (thermal energy) due to friction in the engine / moving parts
3. This means not all input energy is converted to useful kinetic energy, so efficiency must be less than 1 (100%)
4. The wasted energy is spread out into the surroundings (dissipation), making it unavailable for further useful energy transfer
5. The efficiency of the go-kart engine is 0.3 / 30%, meaning 70% of the input energy is wasted

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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-petrol-powered-go-kart-engine-transfers-12-3090f4eb) · Published by Druglandscape Ltd.