If a rod is rotating about one end, does it have pure rotation or do you also consider the translation of centre of mass when calculating its angular momentum?
Also, how would one calculate the angular momentum of a body that is both rotating and translating?
Best Answer
Well, the angular momentum of a rigid body is equal to the sum of the angular momentum of the body around it's center of mass, plus the angular momentum of the center of mass.
Having said that, suppose the rod is rotating about one end (I imagine a pendulum motion; correct me if I'm wrong), you can calculate the angular momentum by $L = I \omega$ if you know the angular velocity $\omega$ and the moment of inertia about the line passing through the axis of rotation.
Suppose you only knew the moment of inertia about the COM. You would then use the parallel axis theorem to calculate the moment of inertia about the new axis. However, most angular momentum tables include moment of inertia about ends of rods also.