A 2.00-kg rock has horizontal velocity of magnitude

A 2.00-kg rock has horizontal velocity of magnitude 12.0 m/s when it is at point Pin Fig. 10.47.

(a) At this instant, what are the magnitude and direction of its angular momentum relative to point O?

(b) If the only force acting on the rock is its weight, what is the rate of change (magnitude and direction) of its angular momentum at this instant?