# A student is investigating how the height from which a ball is dropped affects the depth of the crater it makes in a tray of sand. Explain why the student should drop the ball from each height several times and calculate a mean depth for each height.

> OCR GCSE Physics A: Gateway Science (J249) — P9 Practical skills · Explain · 4 marks

> A student wants to find out whether dropping a ball from a greater height produces a deeper crater in sand. They plan to measure the depth of the crater using a ruler after each drop.

## Mark scheme (4 marks)

1. Repeated measurements identify anomalous results / outliers
2. Anomalous results can be excluded before calculating the mean
3. Repeating and averaging reduces the effect of random error
4. This makes the results more reliable / the mean is a better estimate of the true value

## Key terms

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

## 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-student-is-investigating-how-the-5a11025f) · Published by Druglandscape Ltd.