Find the components along the x, y, z axes of the angular momentum l of a particle, whose position vector is r with components x, y, z and momentum is p with components px, py and pz. Show that if the particle moves only in the x-y plane the angular momentum has only a z-component.
From the given data,
Linear momentum vector,
Position vector,
We have, Angular momentum,
=
=
∴
By comparing respective components, we get,
Since, the particle moves in x-y plane, then the vectors of both position and linear momentum vectors be Zero.
Thus,
Hence, the particle moves in x-y plane the angular momentum acts towards z-direction.