Question

A 2.00-kg rock has a horizontal velocity of magnitude when it is at point P in the Figure.

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?

Answer 1

a)

$$L=mvr\sin{143.1}\\L=(2)(12)(8)\sin{143.1}=115\frac{kgm^2}{s}$$

$$\theta=180-36.9=143.1\degree$$

b)

$$\tau=mgr\cos{36.9}\\\tau=(2)(9.8)(8)\cos{36.9}=125\frac{kgm^2}{s^2}$$