




The angular momentum, L of a point mass is given by 





and the moment of inertia of a point mass, about a point a perpendicular
distance, r away from the line along which it is moving is given by 








therefore 
















and since 











we can write 











Which means that the angular momentum of a point mass is equal to its
linear momentum multiplied by its perpendicular distance from the
point considered. 



Notice that, although we tend to think of bodies
moving in circular paths when we think of angular quantities, we can
calculate the angular momentum of a body, about any point (for
example, point O in the diagram here) even if the body is moving in
a straight line. 


