Fallacy in Work-Energy theorem?? Consider a block moving on a floor which has some friction. It is given an initial velocity of 10 m/s and it comes to rest after some time due to friction. Since friction slows the block down, heat is generated, some of which goes into raising the temperature of the block. Now consider the same above situation in a reference frame of a man moving with a constant velocity of 5 m/s. In this reference frame, the change in kinetic energy is zero... So how do we get from energy conservation that the temperature of the block rises???