# A physics technician records the following measurements during an experiment: a length of 0.0035 m, a mass of 0.000 002 kg, and a time of 15 000 000 ns. Describe how each measurement can be expressed using an appropriate SI prefix, and explain why using SI prefixes is important in scientific communication.

> AQA A-Level Physics (7408) — 3.1.1 Use of SI Units and Their Prefixes · Describe · 5 marks

## Mark scheme (5 marks)

1. 0.0035 m expressed correctly using a prefix (e.g. 3.5 mm or 3500 µm)
2. 0.000 002 kg expressed correctly using a prefix (e.g. 2 µg or 0.002 mg or 2000 ng)
3. 15 000 000 ns expressed correctly using a prefix (e.g. 15 ms or 0.015 s)
4. SI prefixes reduce the number of zeros / make values easier to read or write
5. SI prefixes allow scientists worldwide to communicate measurements consistently / without ambiguity

## Key terms

- [SI prefix](https://www.gradenine.co.uk/glossary/si-prefix)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-physics-technician-records-the-following-016460e3) · Published by Druglandscape Ltd.