# Units and Basic Quantities

## Base Quantities

1. Physical quantities are quantities that can be measure.
2. Each physical quantity contains information on its numerical magnitude and unit of measurement.
3. Physical quantities can be classified into two types,
1. the base quantities
2. the derived quantities
4. Base quantities are quantities that cannot be defined in terms of other base quantities.
5. A base unit is the unit of a base quantity.
6. The following shows the 6 base quantities and the base units.

$\begin{array}{|c|c|c|} \hline \text { Quantity } & \text { Name of unit } & \text { Unit symbol } \\ \hline \text { Length } & \text { metre } & m \\ \hline \text { Mass } & \text { kilogram } & kg \\ \hline \text { Time } & \text { second } & s \\ \hline \text { Electric current } & \text { ampere } & A \\ \hline \begin{array}{c} \text { Thermodynamic } \\ \text { temperature } \end{array} & \text { Kelvin } & K \\ \hline \text { Amount of substance } & \text { mole } & mol \\ \hline \end{array}$

## Derived Quantities

1. Derived quantities are physical quantities derived from a combination of various base quantities through multiplication or division.
2. For example, the area of a rectangle = Width x Length. Both width and length are base quantities, whereas area is a derived quantity as it is derived from length.
3. A derived unit is the unit of a derived quantity. It is the product and/or quotient of the base units.