IIT JEE Advanced 2008 Paper 1

Paragraph for Questions 18–20:
A small block M of mass M moves on a frictionless surface of an inclined plane, as shown in the figure. The angle of the incline suddenly changes from 60° to 30° at point B. The block is initially at rest at A. Assume that collisions between the block and the incline are totally inelastic (g = 10 m∕s2).