# A student pushes a heavy crate across a rough floor. The crate moves at a constant velocity. Explain why the crate moves at constant velocity and describe what happens to the energy that is transferred when the student does work against the resistive force.

> Edexcel A-Level Physics (9PH0) — 8.1 Particle accelerators and detectors · Explain · 5 marks

> A student pushes a heavy crate across a rough floor at constant velocity. The student exerts a horizontal force of 80 N on the crate.

## Mark scheme (5 marks)

1. Constant velocity means the resultant force on the crate is zero
2. The student's pushing force equals the resistive force (friction) in magnitude
3. Work is done against the resistive force (friction)
4. Energy is dissipated / transferred to the surroundings as heat (thermal energy)
5. The total energy is conserved — the energy transferred by the student equals the energy dissipated to the surroundings

## Key terms

- [resistive force](https://www.gradenine.co.uk/glossary/resistive-force)
- [constant velocity](https://www.gradenine.co.uk/glossary/constant-velocity)

## 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-student-pushes-a-heavy-crate-df8066a5) · Published by Druglandscape Ltd.