[填空题]
(a) A yo-yo is made of twos: bn8 +gh)(lv2 dg tl.xcvmx5 solid cylindrimhky7y*x9;()vl htgt) ci,x v cal disks, each of mass 0.050 kg and diameter 0.075 m, joined by a (concentric) thin solid cylindrical hub of mass 0.0050 kg and diameter 0.010 m. Use conservation of energy to calculate the linear speed of the yo-yo when ()*ivxm;ght,cy 7)9xt yklvhit reaches the end of its 1.0-m-long string, if it is released from rest. $m/s$ (b) What fraction of its kinetic energy is rotational? %