Scalar quantities

A physical quantity is something that can be measured. Scalar quantities only have a magnitude or size.

Examples of scalar quantities

Some examples of scalar quantities include:

  • temperature, eg 10 degrees Celsius (°C)
  • mass, eg 5 kilograms (kg)
  • energy, eg 2,000 joules (J)
  • distance, eg 19 metres (m)
  • speed, eg 8 metres per second (m/s)
  • density, eg 1,500 kilograms per metre cubed (kg/m³)

Calculations involving scalar quantities

Adding scalars

The sum of scalar quantities can be found by adding their values together.

Example

Calculate the total mass of a 75 kg climber carrying a 15 kg backpack.

75 kg + 15 kg = 90 kg

Subtracting scalars

Scalar quantities can be subtracted by subtracting one value from another.

Example

A room is heated from 12°C to 21°C using a radiator. Calculate the increase in temperature.

21°C - 12°C = 9°C