1. The problem statement, all variables and given/known data A block of mass m is released from rest on a smooth inclined plane (wedge). The wedge itself is resting on a smooth horizontal surface. The block undergoes a vertical displacement of h. Assume that the height of the incline is h and the length of the incline is h cosec θ Work done by normal reaction force on the block exerted by the wedge is-- (A) Positive (B) Negative (C) Zero (D) Less than mgh in magnitude Work done by normal reaction force exerted by block on the wedge is-- (A) Positive (B) Negative (C) Zero (D) Less than mgh in magnitude More than one choices may be correct. 2. Relevant equations 3. The attempt at a solution I'm so confused over this basic problem. Firstly, I know that the wedge will move a little because it is a smooth surface. Answer to the second question should be positive, because there will be a component of the normal in the opposite direction of the motion of the block. So the wedge will move in the direction of the horizontal component of the normal exerted by the block. But I don't know why the work will be less than mgh. For the first question, I'm very confused.