# A roller coaster car starts from rest at the top of a tall hill and rolls down to the bottom, reaching its highest speed just before the brakes are applied. Explain the energy transfers that take place as the car travels from the top of the hill to the moment it is brought to a complete stop by the brakes, naming all relevant energy stores involved.

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

## Mark scheme (5 marks)

1. The car has gravitational potential energy at the top of the hill (because it is raised / has height and mass)
2. As the car rolls down, gravitational potential energy is transferred to kinetic energy
3. Some energy is also dissipated / transferred to the thermal energy store of the surroundings due to friction / air resistance during the descent
4. When the brakes are applied, kinetic energy is transferred to the thermal energy store of the brakes / surroundings
5. Energy is conserved throughout — it is never created or destroyed, only transferred between stores (law of conservation of energy)

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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