In this chapter, we'll introduce the concepts of velocity and acceleration and apply them to simple situations. By one dimension, one means motion along a line, or in one particular direction. Think of a car going down a straight road, or a person running on a straight track. You could also think of an object being thrown up vertically in the air and watching it fall. It might seem a bit boring at first to work strictly in one dimension. Why not study what happens when a ball is thrown at some other angle besides straight up? Well it's true that its motion is more interesting, but it's also more complicated. One thing that you should try to learn in this course is that it's best to start with something simple and work your way up. We will discuss the more general case of motion in three dimensions, but in order to understand that, it's best to understand motion in one dimension first.