I searched for this problem and could not find satisfactory information or information that applied to my specific concerns. The wedge of mass M is resting on a horizontal surface. A block of mass m is placed on the wedge and the whole system is released from rest. There is no friction anywhere in the system. I have the FBDs complete. I have the newtonian equations of motion in both the x and y components (relative to the table, for an inertial frame) for the wedge and the block. The question asks, use the concept of relative velocities to derive a statement of relative accelerations, then use that to apply the proper constraint. Then, the acceleration of the wedge (relative to the table) and the block (relative to the table and the wedge) must be found. I think I can do this once I get the first part done. Basically the wording of the first part of the question is confusing and I'm not sure where to progress after getting the motion equations. Thanks in advance.