# A student pushes a stationary trolley along a smooth, flat surface. After the push, the trolley moves at a constant velocity. The student claims that because the trolley is now moving at constant velocity, no force acted on it during the push. Explain why the student is wrong, and describe what happened to the trolley's motion and energy during the push.

> Eduqas A-Level Physics — 1.4 Momentum (A-Level only) · Explain · 5 marks

> A stationary trolley is pushed briefly by a student on a smooth, flat surface. After the push, the trolley moves at constant velocity.

## Mark scheme (5 marks)

1. A force must have acted on the trolley during the push because the trolley changed from being stationary to moving (i.e. its velocity changed / it accelerated)
2. Work was done on the trolley by the pushing force (because a force moved the trolley through a distance)
3. The work done transferred energy to the trolley as kinetic energy
4. After the push ends, the surface is smooth so there is no resultant force / no friction, which is why the trolley continues at constant velocity
5. The kinetic energy of the trolley stays constant after the push because no energy is transferred away (smooth surface means no friction / no waste energy transfer)

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](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-stationary-trolley-4e597169) · Published by Druglandscape Ltd.