In studying mechanics, we have generally looked at one object and the forces on it. For most people, the difficult part of mechanics is unlearning the misconception that a moving object needs a force to maintain its motion. (Recall Example 4 in Section 5.D.)
In this chapter we study fluids. A fluid is a large number of interacting particles, so it is somewhat more complicated. The key concept here is pressure. In any given problem you should be thinking, "Do I know the pressure everywhere? Can I figure out the pressure where the crocodile is?" and that sort of thing. Even if pressure is not mentioned in the problem, often it is the concept which leads you to the answer. For instance, when a teenager sips a soft drink through a straw, does he pull the refreshing liquid into his mouth? As you will soon discover, the answer is no.
For the MCAT, you need to know only a few basic principles of elementary fluid mechanics. The tricky part is learning how to apply them in diverse situations. One way to do this is to look at so many examples that any new situation reminds you of something you have seen or worked before. Hence you should pay close attention to the problems and solutions at the end of the chapter.