Energy resources and energy transfers units
- Syllabus
- 2024
- Topic
- —
- Level
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Learning objectives
Choose the correct unit for energy and mechanics quantities
A measurement is complete only when its unit matches the physical quantity. Write the unit symbol after the numerical value, using the correct upper- or lower-case letters.
| Physical quantity | Unit | Unit symbol | Example |
|---|---|---|---|
| mass | kilogram | kg | 2.0 kg |
| energy or work done | joule | J | 150 J |
| distance or displacement | metre | m | 4.0 m |
| speed | metre per second | m/s | 12 m/s |
| acceleration | metre per second squared | m/s² | 9.8 m/s² |
| force | newton | N | 25 N |
| time | second | s | 6.0 s |
| power | watt | W | 60 W |
Match the quantity before choosing the unit. Kilograms measure mass, whereas newtons measure force. Metres measure length, metres per second measure speed, and metres per second squared measure acceleration. Joules measure energy or work done, whereas watts measure power.
Do not choose a unit just because its symbol appears in another unit. m, m/s and m/s² measure three different quantities. Unit symbols are case-sensitive: write J, N and W with capital letters, but kg, m and s in lower case.