A machine part has the shape of a solid uniform sphere of mass 225 g and diameter 3.00 cm. It is spinning about a frictionless axle through its center, but at one point on its equator it is scraping against metal resulting in a friction force of 0.0200 N at that point.
(a) Find its angular acceleration.
(b) How long will it take to decrease its rotational speed by 22.5 rad/s?