Energy and Power

Abstract

As mentioned earlier, in mechanics we use many ordinary English words with special technical meanings, defined more precisely and less generally than in non-scientific use. Typical of such words are “force”, “work”, and “power”. Force has been discussed at length; we now take up the other two. We restrict work to mean that a force has been applied and a displacement has resulted, the situation in which a force produces no motion being one in which no work is done. This is, in effect, restricting ourselves to “useful” work. If you held a brick above your head for an hour, you would probably say you had been “working” hard. Our understanding of the scientific use of the word work can be confused by the fact that the human body is a very complicated mechanism, in which energy is used just to maintain muscular tension even if no “work” in the scientific sense is done. It simplifies thinking of the scientific meaning of the word “work” if it is thought of in terms of machines rather than people.