The property that characterizes the rotatory inertia of an object in motion about the axis which may or may not pass through that specified object is known as angular momentum. One of the best examples of angular momentum is the Earth’s rotation and revolution. For example, the annual revolution that the Earth carries out about the Sun reflects orbital angular momentum while its everyday rotation about its axis shows spin angular momentum.

Angular momentum is broadly categorized into:- 

1. The spin angular momentum. (e.g., rotation)

2. The orbital angular momentum. (e.g. revolution)

The total angular momentum of a body is the sum of spin and orbital angular momentum.

It can be said that angular momentum is a vector quantity, i.e. it requires both magnitude and direction. The angular momentum possessed by a body going through orbiting motion is also said to be equal to its linear momentum. The angular momentum is also given as the product of mass (m) and linear velocity (v) of the object multiplied by the distance (r) perpendicular to the direction of its motion, i.e., mvr. But, in the case of a spinning body, the angular momentum is the summation of mvr for all the particles which make the object.

Some vital things to consider about angular momentum are: 

• Symbol = As the angular momentum is a vector quantity, it is denoted by symbol L.

• Units = It is measured in SI base units: Kg m²s^-1.

• Dimensional formula = M L² T^-1

• Formula to calculate angular momentum (L) = mvr, where m = mass, v = velocity, and r = radius.