[问答题]
A person stands, hands at hia;z3 w1h xb0r g)nfdcxi:gy /7s side px+r)jb91e ob.w9vmk 88ptgx , on a platform that is rotating at a rate of 1.3rev/s If he raises his arms to a horizontal position, Fig. 8–48, the speed of rotatiobekv8xromp91)bgw + p9 .t8jx n decreases to 0.8 $rev/s$ (a) Why?
(b) By what factor has his moment of inertia changed?
