This problem is Kleppner and Kolenkow's 4.7. A ring of mass M hangs from a thread, and two beads of mass m slide on it without friction. The beads are released simultaneously from the top of the ring and slide down opposite sides. Show that the ring will start to rise if m>3M/2, and find the angle at which this occurs. Now is it not the case that, the beads exert a force on the ring which is radial in direction and has a vertical component which is directed downwards always? If that is true how can the ring go up?