My professor has given us the problem and solution here; http://mielsvr1.ecs.umass.edu/mie310/13-176.JPG [Broken] however, he has left out steps. I want to figure out as much on my own as possible, but don't really understand this one. One of the equations written is W (sub ab) = 0, W (sub bc) = 4. However, if the top bar (ab) isn't moving, but the verticle bar (bc) is moving, the block C would just spin in circles. It appears to be going in the X direction only, confined in a track. Any help would be greatly appreciated, especially if you could just translate some equations into words. When I look at them I come up with things like the problem above where they don't seem physically possible or equal. Thanks a bunch in advance.