# A shopping trolley is pushed along a flat supermarket aisle. The shopper pushes the trolley with a constant force. Explain why the trolley moves at a constant velocity rather than continuing to accelerate, and explain what would happen to the trolley's motion if the shopper suddenly stops pushing.

> OCR GCSE Physics A: Gateway Science (J249) — P2.2 Newton's laws · Explain · 4 marks

> A shopper pushes a loaded shopping trolley along a flat supermarket aisle. Despite a constant pushing force being applied, the trolley moves at a constant velocity. When the shopper lets go, the trolley gradually slows down and stops.

## Mark scheme (4 marks)

1. Friction (and/or air resistance) acts on the trolley in the opposite direction to its motion
2. The pushing force is balanced by friction, giving a resultant force of zero
3. By Newton's First Law, an object with zero resultant force continues at constant velocity
4. When the shopper stops pushing, friction is no longer balanced so there is a resultant force acting backwards, causing the trolley to decelerate and stop

## Key terms

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

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](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-450d565b) · Published by Druglandscape Ltd.