[问答题]
A person stands, hands at his side, on a platform that is2aqzsew1q7 cbb* :ufi.h f/v d0(tix9 rotating at a ratci) xh(.pp , -lhyqk/ve of 1.3rev/s If he raises his arms to a horizontal position, Fig. 8–48, the speed of rotation decly .xpihvch ,p/()k q-reases to 0.8 $rev/s$ (a) Why? (b) By what factor has his moment of inertia changed?