The Principle of the Conservation of Energy

Abstract

We can, by our efforts, produce, or assist in producing, a certain transformation in a system: we can displace a body, start it off with a certain velocity, break it, or deform it. On the other hand, we can employ our efforts to place an obstacle in the way of a transformation of the system, to impede the transformation: we can halt a moving body, slow it down, and prevent it being deformed. We [290] say then that we have performed a certain task, done a certain [amount of] mechanical work.