# A shopping trolley is pushed along a flat supermarket floor at a constant velocity. The person pushing the trolley then applies a greater forward force. Explain what happens to the motion of the trolley immediately after the greater force is applied, and describe what eventually happens to the trolley's velocity if the person maintains this greater force.

> Edexcel A-Level Physics (9PH0) — 9.1 Kinetic theory and ideal gases · Explain · 5 marks

> A shopping trolley moves at a constant velocity across a flat supermarket floor when a constant forward force is applied. The person pushing the trolley then increases the forward force.

## Mark scheme (5 marks)

1. At constant velocity, the forward force is equal to (balanced by) the friction/resistive force, giving a zero resultant force.
2. When the greater force is applied, the forward force is now greater than the friction/resistive force, so there is a resultant force in the forward direction.
3. The resultant force causes the trolley to accelerate (speed up / increase in velocity).
4. As the trolley speeds up, the friction / resistive force acting on it increases.
5. Eventually the friction/resistive force equals the new greater forward force, giving a zero resultant force, so the trolley reaches a new higher constant velocity.

## Key terms

- [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-shopping-trolley-is-pushed-along-d187df97) · Published by Druglandscape Ltd.