Two particles each of mass `m` and speed `v`, travel in opposite direction along parallel lines separated by a distance d. Show that the vector angular momentum of this system of particles is the same about any point taken as origin.

Explanation

Angular momentum of two particle system about pt A on `X_(1)X_(2)`
`vecL_(A)= mvec vxx 0+ m vecv xx d= m vec vd`
Angular momentum of two particle system about pt. B on `Y_(1)Y_(2)` is
`vecL_(B)= m vecv xx d xx mvec vxx0= m vecvd`
Angular momentum of two particle system about O is
`vecL_(0)= m vec v x+ m vec v(d-x)= m vec v d`
Thus, `vecL_(A)= vecL_(B)=vecL_(0)` (Hence proved)