 So now that we've seen position, velocity, and acceleration, we can come back to the graphs and figure out how to interpret all of these things from just the position graph. We're going to start with a pretty simple position versus time graph here with just some straight line segments. I'll remind you that positive positions means you're somehow in front of the reference point, and negative positions means you're somehow behind the reference point. For this graph, that's the two sections that we've got here above and below the x-axis. Anytime you cross the x-axis, that means you're actually at your reference point at that particular time. We can learn a lot more from these position versus time graphs. For example, these sections here where you've got a nice horizontal segment, well that means you've got constant position or you're standing still. That means you're not moving or your velocity is equal to zero there as well. If you're moving forward, then you should have a slope moving up along your graph. And if you're moving backwards, you should have a slope going downwards on your graph. In this case is because they're nice straight line segments, not only are you moving forward, but you're moving forward at a constant velocity. And here you're moving backward at a constant negative velocity. If we've got curved sections on our graph, we can learn even more from that. So for example, if we're moving forward, again, we've got our upward slope. Since it's not a straight line, it's not a constant velocity during that particular segment. But anytime we're moving forward, we're going to be sloped upwards. If you're sloped upwards a little steeper, that means you're moving faster in the forward direction. If you're a little bit less slope, that means you're moving forward but not quite as fast. Similarly, if you're moving backwards, you're going to have a negative slope on that particular section of the graph like we have in these two points. Now if we get one of these points up here on top, it's not a flat line, but the curve does flatten out there. And if you look at it, we're going from moving forward to moving backwards as we're going through that. So this is a place where we're changing direction. And as we go through that particular position, we've got moving from a positive velocity to a negative velocity, so you must go through zero at that point. So it's like standing still, but rather than stopping and staying stopped, you're moving forward and moving backwards and just momentarily right in between you stop. And that's going to happen anytime we've got one of these inflection points where the curve flattens out. Now we can learn about our acceleration from these graphs, too. So for example, positive acceleration is going to happen when this curve is facing upwards. We've got another section over here where we've also got positive acceleration. In comparison, negative acceleration, we've got a curve and the curve is facing downwards. So anytime you've got a downward facing curve, not only do you know it's accelerating, but it's accelerating with a negative acceleration. If you do happen to have some segments where it is flattened out, that means you've got constant velocity or no acceleration, so there's no curve where you've got straight lines. So for the position versus time graph, the positive and negative lets you know where you are relative to your reference point. Constant positions or no velocities are horizontal sections. If I've got constant velocity, that's a straight slope with an upward slope being positive velocities, a downward slope being negative velocities. And if you've got curved segments, that means you do have an acceleration. Curve facing upwards is a positive acceleration and curve facing downwards is a negative acceleration. So that's how you can work on interpreting position versus time graphs.