Define angular momentum.

Explanation

(i) The angular momentum of a point mass is defined as the moment of its linear momentum. In other words, the angular momentum L of a point mass having a linear momentum p at a position r with respect to a point or axis is mathermatically written as,
`vec(L) = vec(r) xx vec(p)`
(ii) The magnitude of angular momentum could be written as, L = r p sin `theta`
where, `theta` is the angle between `vec(r) and vec(p).vec(L)` is perpendicular to the plane containing `vec(r) and vec(p)`
(iii) As we have written in the case of torque, here also we can associate `sin theta` with either `vec(r) and vec(p)`
`{:(L = r (p sin theta) = r(p bot)),(L = (r sin theta)p = (r bot)p):}`
where, `p bot` is the component of linear momentum p perpendicular to r, and `r bot` is the component of position r perpendicular to p.
(iv) The angular momentum is zero (L = 0), if the linear momentum is zero (p = 0) or if the particle is at the origin `(vec(r) = 0)` or if `vec(r) and vec(p)` are parallel or antiparallel to each other `(theta = 0^(@) or 180^(@))`