[问答题]
A person stands, handscynj5 ol3 lo70 at h.kyyrayw-) qhl sx091 is side, on a platform that is rotating at a rate of 1.3rev/s If he raises his arms to a horizontal position, ly.yqa0yw1h s-k r9x) Fig. 8–48, the speed of rotation decreases to 0.8 $rev/s$ (a) Why? (b) By what factor has his moment of inertia changed?