 Now we have the concept of average velocity. Velocity in general means how fast and what direction is an object moving. That means it's a vector quantity because it has magnitude and direction. It has dimensions of type length per time. And specifically, our standard metric unit is going to be meters per second. Now, average velocity is a little bit more specific. It's the velocity averaged over a time period. Turns out this is related to the displacement in the time span because the average velocity is the displacement, delta x, divided by the time span, delta t. And that gives me my average velocity, where velocity is given by a v with the vector symbol over it. And the average is shown using a subscript of AVG. If I expand out what the delta x and the delta t mean, I can write this out in terms of the initial and final positions and times according to this equation. Now, we can also look at this graphically. If I've got a series of positions and times, I can find the average velocity between any two points on this graph. So let's say, for example, I wanted to look at one second and four seconds. Well, I've got two points here on the graph, which represent one second and four seconds. And from the graph, I can determine both the time span, three seconds. And from the graph, I can find the displacement. In this case, I went from 2 meters up to 5 meters. So that's a displacement of 3. If I connect those two points with a line, what I see is that the slope of the line, which is defined as the rise over the run, is our average velocity because the rise is the delta x and the run is the delta t. So I can find the average velocity between any two points on the graph by drawing a line between those two points and calculating the slope. In this case, my increase was 3 meters and my time span was 3 seconds. So I have an average velocity of 1 meter per second. If I take a look at some example word problems, I can see how I can use my formulas. In this case, I've got the ball's position being tracked as it rolls across the desk. And I'm given two specific points. At 3 seconds, it was at 6 meters. And at 5 seconds, it was at a position of 7 meters. So it makes sense to use my expanded version of the average velocity equation. And to take the specific data points I have for my initial time and position and my final time and position and plug those into my equation. If I plug those in, you can check the math later, but this gives me 0.5 meters per second because I moved a displacement of 1 meter in 2 seconds time. Now sometimes you're given a word problem where you don't have as much information. You don't have the specific positions and the specific times that you're looking at. In these cases, you can just figure out, well, the total time it took was 10 seconds. And the total displacement was 15 meters. We use the units to help us figure out which ones goes into which place here. When I use my equation for my average velocity then, I can see that the average velocity for this period where it went 15 meters forward in 10 seconds is 1.5 meters per second. Here's another problem where it seems like I have even less information given to me. I can definitely tell that my time period is 1 hour, but it gives me no information about how far anything is. Well, if you read the problem carefully, we don't have to know how far it is from the dorm room to the cafeteria because the main point is that they went from their dorm room back to their dorm room. So their net displacement over this entire time period of the hour is 0. That means their average velocity is 0 miles per hour. Now, they moved during that time, but since this is an average, part of the time they were going in one direction, part of the time they're going back in the other direction, part of that's going to be positive and part of it's going to be negative and averaged out over the time span. That gives me an average of 0. So this ends up our quick concept of the average velocity. You'll get lots more practices. We move through the physics course.