# A student measures the acceleration of a toy car rolling down a ramp. She times how long the car takes to travel a fixed distance and repeats the measurement six times. Her results, in seconds, are: 1.23, 1.25, 1.24, 1.26, 1.58, 1.24. Explain how the student should process these results to obtain a reliable value for the time, and explain why her final value may still not be accurate.

> AQA A-Level Physics (7408) — 3.1.2 Limitations of Physical Measurements · Explain · 5 marks

## Mark scheme (5 marks)

1. Identify 1.58 s as an anomalous result (anomaly / outlier)
2. The anomalous result should be excluded / not included in the mean
3. Calculate a mean (average) of the remaining results
4. The result may still be inaccurate because of a systematic error
5. Systematic error affects all readings in the same way / cannot be reduced by averaging

## Key terms

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

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-measures-the-acceleration-of-f45805ec) · Published by Druglandscape Ltd.