Consider a block that is to be lifted by a wedge. As the wedge slides under the block, the block slides up the sloped side of a wedge. This lifts the weight F B of the block. The horizontal force F A needed to lift the block is obtained by considering the velocity of the wedge v A and the velocity of the block v B. If we assume the wedge does not dissipate or store energy, then the power into the wedge equals the power out.