# A heavy wooden crate is pushed across a rough concrete floor at a constant velocity by a warehouse worker. Explain why the worker must continue to apply a force to keep the crate moving at constant velocity, and describe what would happen to the motion of the crate if the worker suddenly doubled the pushing force.

> Edexcel GCSE Physics (1PH0) — 9.1 Forces and their effects · Explain · 4 marks

> A warehouse worker pushes a heavy wooden crate across a rough concrete floor. The crate moves at a constant velocity.

## Mark scheme (4 marks)

1. Friction acts as a resistive contact force opposing the motion of the crate
2. At constant velocity the pushing force and friction are equal / balanced, giving a resultant force of zero
3. If the worker doubles the pushing force, there is now a resultant force in the direction of motion (the pushing force is greater than friction)
4. The resultant force causes the crate to accelerate / speed up in the direction of the push

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](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-heavy-wooden-crate-is-pushed-174abaf5) · Published by Druglandscape Ltd.