Angular momentum of an object revolving around an external axis O is equal to the cross-product of the position vector with respect to O and its linear momentum.

${\vec {L}}=I{\vec {\omega }}$

Angular momentum of a rotating object is equal to the moment of inertia times angular velocity.

Force and linear momentum, torque and angular momentum[edit]

We'll take two particles, say, a and b. Their momentums are ${\vec {p}}_{a}$ and ${\vec {p}}_{b}$.They are moving opposite to each other along the x-axis and they collide. Now force is given by:

Mass(m): A quantity that describes how much material exists, or how the material responds in a gravitational field. Mass is a measure of inertia. (kg)

Velocity (v): Displacement divided by time (m/s)

Angular momentum (L): A vector quantity that represents the tendency of an object in circular or rotational motion to remain in this motion. (kg·m^{2}/s)

Moment of inertia (I): A scalar property of a rotating object. This quantity depends on the mass of the object and how it is distributed. The equation that defines this is different for differently shaped objects. (kg·m^{2})

Angular speed (ω): A scalar measure of the rotation of an object. Instantaneous velocity divided by radius of motion (rad/s)

Angular velocity (ω): A vector measure of the rotation of an object. Instantaneous velocity divided by radius of motion, in the direction of the axis of rotation. (rad/s)

Force (F): mass times acceleration, a vector. Units: newtons (N)

Time(t): (s)

Isolated system: A system in which there are no external forces acting on the system.

Position vector (r): a vector from a specific origin with a magnitude of the distance from the origin to the position being measured in the direction of that position. (m)