A small mass m is attached to a massless string whose other end is fixed at p as shown in the figure. The mass is undergoing circular motion in the x-y plane with centre at 0 and constant angular speed ω. If the angular momentum of the system, calculated about o and p are denoted by Lo and Lp respectively, then
Lo remains constant while Lp varies with time.
Lo remains constant while Lp varies with time because the direction of angular momentum keeps on changing.