[问答题]
A person stands, handa87n95rt ua*(/lvx4c dtxv svs at v)kg y8xbnx,8his side, on a platform that is rotating at a rate of 1.3rev/s If he raises his arms to a 8,n vy)x xg8bkhorizontal position, 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?