Say there is a hollow can of radius R and length L with a small hole drilled through the center of the lid. A massless, taut string of length l is strung through the hole, and it connects two spiders. L>>l. One spider of mass m is confined to the outer/topside of the lid, while the other spider of mass M is confined to the inside walls of the can. Can we conclude that the momentum associated with the center of mass vector is conserved, and if so can we move the frame of reference to the center of mass