# A student wants to find the average diameter of a human hair. Explain why the student should measure the total width of several hairs pressed tightly together side by side, rather than measuring a single hair directly with a ruler.

> Cambridge International IGCSE Physics (0625) — 1.1 Physical quantities and measurement techniques · Explain · 4 marks

## Mark scheme (4 marks)

1. A single hair is too thin / too small to measure accurately with a ruler
2. Measuring several hairs together gives a larger / measurable total width
3. The total width is divided by the number of hairs to give the width / diameter of one hair
4. This reduces the percentage uncertainty in the measurement / gives a more accurate result

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-wants-to-find-the-c8fe89f8) · Published by Druglandscape Ltd.