### Theory:

A physical quantity is a property of a material or system that can be quantified by measurement.
Example:
The physical quantity mass can be measured in kg.
The physical quantities are classified into two types, they are
•  Fundamental quantities.
•  Derived quantities.
Fundamental quantities: - is a set of quantities, which cannot be expressed in terms of any other quantities, and the corresponding units are known as fundamental units. In physics, there are seven fundamental physical quantities, which are measured in base units - SI units, or fundamental physical units. They are listed as follows:
• Length: The SI unit of  the length is metre and it is denoted as 'm'.
• Mass: The SI unit of  the mass is kilogram and it is denoted as 'kg'.
• Time: The SI unit of  the time is second and it is denoted as 's'.
• Temperature: The SI unit of the tempearture is kelvin and it is denoted as 'K'.
• Electric current: The SI unit of the electric current is ampere and it is denoted as 'A'.
• Amount of substance: The SI unit of the amount of asubstane is mole and it is denoted as 'mol'.
• Luminous instensity: The SI unit of the luminous intensity is candela and it is denoted as 'cd'.

Derived quantities : - is nothing but, physical units made by mathematically multiplying, dividing and/or combining the fundamental units. The corresponding units are known as derived units. The following are the derived units :
• Area: The SI unit of  the area is 'metre²' and it is denoted as ''.
• Volume: The SI unit of  the volume is 'metre³' and it is denoted as ''.
• Speed: The SI unit of the speed is 'metre/second' and it is denoted as 'm/s'.
• Electric charge: The SI unit of the electric charge is 'ampere $$×$$ second' and it is denoted as 'coulomb'.
• Density: The SI unit of the density is 'kilogram/metre³' and it is denoted as 'kg/m³'.