There are a number of technical terms in physics that have a nontechnical equivalent in ordinary usage. An example we saw in the previous chapter is force. We can talk about force in conversation without meaning a push or a pull that changes the velocity of an object, but it’s easy to see that that technical definition has something in common with the ordinary use of the word force. The same is true with work, energy, and power. All three of these words have familiar connotations in ordinary speech, but in physics they take on a technical meaning. As with force, the ordinary meaning of these words provides us with some hint as to their meaning in physics. However, we shouldn’t rely too heavily on our intuition, since, as we shall see, there are some significant divergences from what common sense tells us. The related phenomena of work, energy, and power find their way into a good number of questions on SAT II Physics. And energy, like force, finds its way into almost every aspect of physics, so a mastery of this subject matter is very important. The conservation of energy is one of the most important laws of physics, and conveniently serves as a tool to sort out many a head-splitting physics problem.