Angular momentum is defined as the moment of linear momentum of a particle. The moment of linear momentum is equal to mass times velocity crossed with radius (mv x r). This can also be written as mass times radius squared times angular velocity (mr^2ω), which is equal to the moment of inertia (I) times angular velocity. Moment of inertia is a measure of a particle's inertia during circular motion and is calculated as the mass times the square of its distance from the axis of rotation. Angular momentum is then equal to the moment of inertia times the angular velocity.

1. Angular momentum
Angular momentum of a particle is defined as the moment
of linear momentum of the particle.
The moment of linear momentum = mv X r
= mr X r, ( v = r)
= mr2
= I 

where I = mr2 is called the moment of inertia of the rotating
particle.

2. Moment of inertia is the measure of inertia of the particle in
circular motion and it is equal to the product of the mass of
the particle and the square of its distance from the axis of
rotation.
Angular momentum, L = I 

Angular momentum = moment of inertia X angular velocity
The unit of angular momentum is kg m2 s–1

3. Comparison of linear and angular motion
No. Linear motion Angular motion
1 Linear displacement is ‘s’ Angular displacement is ‘θ’
2 Linear velocity, v = Angular velocity, =
3 Linear acceleration, a =
Angular acceleration,
 =
4
Mass ‘m’ is the measure of
inertia in linear motion
Moment of inertia I = mr2, is
the measure of inertia in
circular motion
5 Linear momentum, p = mv Angular momentum, L = I 
S
t
V - U
t

t
 - 
t