Q.What are fundamental quantities? Give an example.

Fundamental quantities are the independently defined base physical quantities from which all other (derived) quantities are built; the SI system recognises seven of them.

In physics, physical quantities are classified into two types:

1. Fundamental (base) quantities — quantities that stand on their own and are not defined in terms of any other physical quantity. Their units are called fundamental (or base) units.

2. Derived quantities — quantities that are defined in terms of the fundamental quantities (e.g. velocity = length/time), with correspondingly derived units.

The SI system has seven fundamental quantities and their base units:

• Length (metre, m)
• Mass (kilogram, kg)
• Time (second, s)
• Electric current (ampere, A)
• Thermodynamic temperature (kelvin, K)
• Amount of substance (mole, mol) …