[问答题]
A person stands, hands at his s(u/,cec o5 qw bage5r1ide, on a platform that is rotating at a rate od*th:1/: tn +oplad ewf 1.3rev/s If he raises his arms to a horizontal position, Fig. 8–48, l/h wtp:+1n do:t aed*the speed of rotation decreases to 0.8 $rev/s$ (a) Why?
(b) By what factor has his moment of inertia changed?
