# A seesaw in a playground has a pivot at its centre. A child of weight 400 N sits 1.5 m from the pivot on one side. An adult wants to balance the seesaw by sitting on the other side, closer to the pivot than the child. Explain, using the principle of moments, why the adult must sit closer to the pivot than the child.

> Eduqas GCSE Physics — 3.3 Moments, levers and gears · Explain · 4 marks

> A seesaw is balanced when the turning effects on each side of the pivot are equal.

## Mark scheme (4 marks)

1. The moment (turning effect) depends on both the force and the perpendicular distance from the pivot
2. For the seesaw to balance, the moments on each side must be equal (principle of moments)
3. The adult has a greater weight (force) than the child
4. Because the adult's force is larger, the distance must be smaller to produce the same moment as the child

## Key terms

- [moment](https://www.gradenine.co.uk/glossary/moment)
- [pivot](https://www.gradenine.co.uk/glossary/pivot)
- [principle of moments](https://www.gradenine.co.uk/glossary/principle-of-moments)

## Related

- [Revision notes for Eduqas GCSE 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-seesaw-in-a-playground-has-8d56acef) · Published by Druglandscape Ltd.