# A small toy car is wound up by compressing a spring inside it. When released on a flat surface, the car moves forward and gradually slows to a stop. Explain the energy transfers that take place from the moment the spring is released until the car stops moving.

> WJEC A-Level Physics (Wales) — 1.3 Energy concepts · Explain · 5 marks

## Mark scheme (5 marks)

1. The compressed spring stores elastic potential energy
2. As the spring releases, elastic potential energy is transferred to kinetic energy of the moving car
3. As the car moves, friction acts between the wheels/axle and the surface, causing a waste energy transfer
4. Kinetic energy is transferred to thermal/heat energy in the surroundings (dissipated)
5. Energy is conserved throughout — the total energy in the closed system remains the same, it is only transferred/dissipated, not created or destroyed

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-small-toy-car-is-wound-ed56e16d) · Published by Druglandscape Ltd.