# A roller coaster cart starts from rest at the top of a hill and travels down to the bottom. Explain the energy transfers that occur as the cart moves from the top of the hill to the bottom, and explain why the kinetic energy of the cart at the bottom is always less than the gravitational potential energy it had at the top.

> Edexcel A-Level Physics (9PH0) — 2.3 Energy and work done · Explain · 5 marks

> A roller coaster cart of mass 500 kg starts from rest at the top of a hill that is 20 m above the ground. The cart rolls down to ground level. The track is not smooth.

## Mark scheme (5 marks)

1. The cart has gravitational potential energy (GPE) at the top of the hill
2. As the cart moves down, gravitational potential energy is transferred to kinetic energy
3. Friction (between cart and track) / air resistance acts on the cart as it moves
4. Work is done against friction / air resistance, transferring energy to the thermal energy store of the surroundings / track / cart
5. Because some GPE is transferred to thermal energy (not to kinetic energy), the kinetic energy at the bottom is less than the original GPE

## Key terms

- [gravitational potential energy](https://www.gradenine.co.uk/glossary/gravitational-potential-energy)
- [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-roller-coaster-cart-starts-from-1419834f) · Published by Druglandscape Ltd.