[问答题]
A large spool of rope r3b 9 ff71tcxe6d2lxzrolls on the 3 - 5fo *mlifyjjij7f5ground with the end of the rope lying on the top edge of the spool. A person grabs the end of the rope and walks a distance L, holding onto it, Fig. 8–50. The spool rolls behind the person without slipping. What -7ii*mjj y5jf53flof length of rope unwinds from the spool? How far does the spool’s center of mass move?