 Now we've got motion diagrams. When we think about representing motion, there are several different ways we can do this. We've already talked about motion versus time graphs, and they can show you a lot of information, but they don't always make sense to students when they're first starting. You can talk about movies and animations, which are great if you're watching a video, but they're kind of hard to put down in the textbook or to put on your paper to turn into your teacher. So we have another thing called motion diagrams, or sometimes they're called dot diagrams, to represent the motion. So we want to explain what those are doing. So to help with this, I want you to meet Al. Al can walk, he can run, he can run really fast, he can even stand still. But no matter where Al is, we're going to represent his position with a dot. So here we're starting out with some forward motion. So I've got Al, and for each second I can represent where he is with a dot on the number line. As he walks forward, you see he's covering some distance. His position is changing, and so I've got a new dot for each second that he's moving. Now I'm going to simplify this a little bit by looking at just those dots. So these are the same dots we had on the diagram before. I can then connect those with arrows. Each arrow represents how he moved from one second to the next. And therefore those arrows can represent the velocity, the motion, the displacement moved in a certain amount of time. Now if I've got equally spaced dots like I did before, that means my arrows between them are all equal lengths. And since the arrows represented velocities, that means I've got a constant velocity. The other way you can think of this is that in constant velocity you move the same distance so there's equal spacing between each of those dots. Well we can also compare velocities. Started out with Al walking, now he's running. And you'll notice that each second he's covering a lot more distance than he did when he was just walking. So that means our dots are spaced much further apart. Or you can think of it as the arrows are much longer. In either case that means you've got a higher velocity. You've moved a longer distance in that same amount of time. So remember, dots that are further spaced apart represent higher velocities. Dots that are closer together represent smaller velocities. We can now look at changing velocities. We're first going to start with Al slowing down. So here he starts out with much larger spacings and progressively gets to much much shorter spacings. Meaning he's moving much slower over here than he was over here when he was moving much faster. We can look at the same sort of thing with Al speeding up. In this case he's starting out much closer together and ending up much further apart. So we start with much smaller velocities and we end up with much larger velocities. Now these diagrams work pretty well if you're just moving in one dimension and you're moving only in the forward direction. If we were changing directions or moving backwards you can't just use the dots. You'd have to use the arrows as well. And if you change directions they would overlap and that gets very confusing. But if we're just moving forward it's a really easy way to quickly look at that motion and understand our velocities. So these motion diagrams are just one more tool that we can use to understand motion in one dimension.