FUNDAMENTAL AND DERIVED UNITS

 Any unit of mass,length,and time in mechanics is called a fundamental,absolute or base unit.Other units which can be expressed in terms of fundamental units are called derived units.

System of units :A complete set of units ,both fundamental and derived for all kind of physical quantities is called system of units.

(1)CGS system (2)MKS system (3)FPS system

(4)S.I. system : It is known as International system of units.There are seven fundamental quantity in this system.These quantities and their units are given in the following table.

physical quantity	unit	abbreviation
mass	kilogram	kg
length	meter	m
time	second	s
temperature	Kelvin	K
amount of substance	mole	mol
electric current	ampere	A
luminous intensity	candela	cd

Besides the above seven fundamental units two supplementary units are also defined- Radian(rad) for plane angle and steradian(sr) for solid angle