A string is wrapped around a uniform disk of mass M and radius R. Attached to the disk are four low-mass rods of radius b, each with a small mass m at the end (see figure below). ●m m b: M, R m m F W F The apparatus is initially at rest on a nearly frictionless surface. Then you pull the string with a constant force F. At the instant when the center of the disk has moved a distance d, an additional length w of string has unwound off the disk. (Use any variable or symbol stated above as necessary.) (a) At this instant, what is the speed of the center of the apparatus? VCM,f= Explain your approach. I applied the energy principle to the disk only. I applied the energy principle to the small masses only. I applied the energy principle to the system as a point particle. I applied the energy principle to the system as an extended object. (b) At this instant, what is the angular speed of the apparatus? wf= Explain your approach. I applied the energy principle to the disk only. I applied the energy principle to the small masses only. I applied the energy principle to the system as a point particle. I applied the energy principle to the system as an extended object.