# A delivery worker lifts a heavy parcel from the ground and places it onto a shelf. The parcel is then pushed horizontally along the shelf at a constant speed until it reaches the edge, where it falls off and lands on the floor below. Explain the energy transfers and transformations that occur from the moment the worker begins to lift the parcel to the moment it hits the floor.

> Edexcel A-Level Physics (9PH0) — 2.3 Energy and work done · Explain · 5 marks

## Mark scheme (5 marks)

1. Work is done by the worker on the parcel as it is lifted, transferring energy to the parcel's gravitational potential energy store.
2. When the parcel is pushed horizontally at constant speed, work is done against friction, transferring energy to the thermal energy stores of the parcel and shelf.
3. The gravitational potential energy store of the parcel decreases as it falls from the shelf.
4. The gravitational potential energy store is transferred to the kinetic energy store of the parcel as it falls (it speeds up).
5. When the parcel hits the floor, the kinetic energy store is transferred to the thermal energy stores (and sound) of the parcel and floor.

## 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-delivery-worker-lifts-a-heavy-cf3c3a52) · Published by Druglandscape Ltd.