# A bicycle tyre is pumped up and then left in a cool garage overnight. A cyclist notices that the tyre feels less firm in the morning compared to just after pumping. Using kinetic theory, explain why the pressure inside the tyre decreases as the temperature of the air inside falls.

> WJEC GCSE Physics (Wales) — 2.2 The kinetic theory and gas pressure · Explain · 4 marks

## Mark scheme (4 marks)

1. As temperature falls, the average kinetic energy of the gas molecules decreases
2. The molecules hit the walls of the tyre with less force (per collision)
3. The molecules collide with the walls less frequently
4. Less force per unit area on the tyre walls means lower pressure (linking reduced collisions/force to lower pressure)

## Key terms

- [kinetic theory](https://www.gradenine.co.uk/glossary/kinetic-theory)
- [pressure](https://www.gradenine.co.uk/glossary/pressure)
- [temperature](https://www.gradenine.co.uk/glossary/temperature)

## Related

- [Revision notes for WJEC GCSE 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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Source: [GradeNine](https://www.gradenine.co.uk/q/a-bicycle-tyre-is-pumped-up-885e33f2) · Published by Druglandscape Ltd.