\(\def \u#1{\,\mathrm{#1}}\) \(\def \abs#1{\left|#1\right|}\) \(\def \ast{*}\) \(\def \deg{^{\circ}}\) \(\def \ten#1{\times 10^{#1}}\) \(\def \redcancel#1{{\color{red}\cancel{#1}}}\) \(\def \BLUE#1{{\color{blue} #1}}\) \(\def \RED#1{{\color{red} #1}}\) \(\def \PURPLE#1{{\color{purple} #1}}\) \(\def \th#1,#2{#1,\!#2}\) \(\def \lshift#1#2{\underset{\Leftarrow\atop{#2}}#1}}\) \(\def \rshift#1#2{\underset{\Rightarrow\atop{#2}}#1}}\) \(\def \dotspot{{\color{lightgray}{\circ}}}\)

Motion Diagrams

Kinematics is the study of how things move, and so in this chapter we will look at several ways to describe and understand motion. Motion diagrams are one way to do this.

Imagine a car which is moving to the right at a constant velocity. Now suppose we take a picture of the car at regular time intervals, and superimpose the pictures. It might look something like this

Here is a car which is speeding up as it moves to the right.

If we were doing this on paper, drawing all those little cars would get tedious. So instead we replace the pictures with dots.

Now this isn't quite good enough. For one thing, we can't tell if the car is speeding up to the right or slowing down to the left, or maybe it's hopping around from spot to spot. We need to specify the order in which the dots appear. We can do this by drawing an arrow from one dot to the next, or by labelling the dots by the time at which the dot appears. Or both!

This is called a motion diagram.