# A student investigates how the speed of a trolley changes with the height of the ramp it rolls down. She plans to change the height of one end of the ramp and measure the speed of the trolley at the bottom each time. Describe how the student should make her investigation valid and how she should ensure her results are reliable. Include in your answer what she should do with any anomalous results.

> Edexcel A-Level Physics (9PH0) — 1.1 Practical and investigative skills · Describe · 5 marks

> A student uses a ramp and a trolley to investigate how the height of a ramp affects the speed of the trolley at the bottom. She measures height in centimetres and speed in metres per second.

## Mark scheme (5 marks)

1. Keep all other variables constant / control variables (e.g. keep the mass of the trolley the same / keep the length of the ramp the same / keep the surface of the ramp the same)
2. Repeat each measurement (at each height) at least three times
3. Calculate a mean (average) speed from the repeated readings
4. Identify anomalous results by checking whether a value is significantly different from the other repeated readings
5. Exclude anomalous results from the calculation of the mean (do not include them when averaging)

## Key terms

- [valid](https://www.gradenine.co.uk/glossary/valid)
- [reliable](https://www.gradenine.co.uk/glossary/reliable)
- [anomalous result](https://www.gradenine.co.uk/glossary/anomalous-result)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-investigates-how-the-speed-dcb8bbb6) · Published by Druglandscape Ltd.