A small block starts from rest at point A and slides without friction down a circular track of radius 2R. At point B (the lowest point on the track), it enters another frictionless circular track, which has a radius R. Positions of the block along this second track can be described in terms of the angle 0 measured from the horizontal line through C. (Treat the block as a point mass.) D. 2R (a) When the block passes point B, think about how the normal force N exerted by the track on the block must be varying as the block ascends. Argue qualitatively that the block cannot drop off the track before it reaches point C, and that it must drop off the track before it reaches point D. Now

A small block starts from rest at point A and slides without friction down a circular track of radius 2R. At point B (the lowest point on the track), it enters another frictionless circular track, which has a radius R. Positions of the block along this second track can be described in terms of the angle 0 measured from the horizontal line through C. (Treat the block as a point mass.) D. 2R (a) When the block passes point B, think about how the normal force N exerted by the track on the block must be varying as the block ascends. Argue qualitatively that the block cannot drop off the track before it reaches point C, and that it must drop off the track before it reaches point D. Now