試題詳解

10. A merry-go-round of radius R = 2.0 m has a moment of inertia I = 250 kg-m², and is rotating at 10 rpm. A child whose mass is 25 kg jumps onto the edge of the merry-go-round, heading directly toward the center at 6.0 m/s. The new angular speed (in rpm) of the merry-go-round is approximately
(A)10
(B)9.2
(C) 8.5
(D)7.1
(E)6.4