A box and it's contents have a total mass M. A string passes through a hole in the box and you pull on the string with a constant force F (this is in outer space there are no other forces acting).

a) Initially the speed of the box was Vi. After the box had moved a long distance w, your hand moved an additional distance d ( a total distance of w+d), because additional string of length d came out of the box. What is now the speed of the box?

b) If we could have looked inside the box, we would have seen that the string was wound around a hub that turns on an axle with negligible friction. Three masses each of mass m, are attached to the hub at a distance r from the axle. Initially the angular speed relative to the axle was wi. In terms of given quantities, what is the final angular speed relative to the axis, wf?