If the position of the 3-kg collar C on the smooth rod AB is held at r = 720 nun, determ...

If the position of the 3-kg collar C on the smooth rod AB is held at r = 720 nun, determine the constant angular velocity at which the mechanism is rotating about the vertical axis. The spring has an unstretched length of 400 mm. Neglect the mass of the rod and the size of the collar.