# A person pushes a heavy box along a horizontal floor at a constant speed. Explain why the person must continue to do work on the box even though its speed is not changing.

> Cambridge International IGCSE Physics (0625) — 1.7 Energy, work and power · Explain · 4 marks

## Mark scheme (4 marks)

1. Friction acts on the box, opposing its motion
2. A force must be applied to balance / overcome friction so that the resultant force is zero
3. Work is done when a force moves an object in the direction of the force
4. The work done is transferred as thermal energy (heat) due to friction / energy is dissipated against friction

## Key terms

- [work](https://www.gradenine.co.uk/glossary/work)
- [constant speed](https://www.gradenine.co.uk/glossary/constant-speed)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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-person-pushes-a-heavy-box-a88c9eec) · Published by Druglandscape Ltd.