A uniform, solid cylinder with mass 2M and radius 2R rests on a horizontal tabletop. A massless string is attached to a massless yoke which is in turn attached to a frictionless axle that runs through the central axis of the cylinder, so that the cylinder can rotate about the axle. The string passes over a solid cylindrical pulley with mass M and radius R that is mounted on a frictionless axle. A block of mass M is suspended from the free end of the string. The string does not slip over the pulley surface, and the cylinder rolls without slipping on the tabletop. Use energy methods to derivean expression for the speed of the block after it has descended a distance d.