I've never been too clear on some aspects of waste heat. I know the law of conservation of energy says that the amount of energy must remain constant, but my confusion comes from exactly what form it ends up taking. As an example if I swing a hammer and hit something I know that chemical energy is transformed to kinetic energy in my arm, which is then transformed to heat in the object I hit, as well as the sound of it being hit, and the work of deforming the object slightly. The question I have though is does all that energy end up simply becoming heat? I know that sound is just movement of air, so it would seem logical that it would become heat through friction, is that so? Then as for the actual work of deforming the object where does the energy that went into doing that go? Is that in fact where the heat came from? To give another example, say I moved some weight over a horizontal distance, where does the energy I burn go? Is it all transferred to heat? Is it the same heat that warms my muscles? It seems like the energy that escapes the inefficiencies of my body and actually does the work couldn't then warm my muscles, so the question then is where does that energy go? One last example which is different from the previous ones. In a car when you are in neutral is more heat produced in the engine since no work is being done? I assume the engine burns a constant amount of gas at a certain rpms since the same chemical energy is being turned into heat, but without then doing any work more must remain as heat in the engine right? Then if the car is in gear and in motion I assume that extra heat is being turned into kinetic energy and then being lost to friction and drag, and thus becoming heat again. I guess in summery what I'm asking is does all energy end up as heat, or is there another form of waste energy?