Welcome back. So in the last video, we were talking about describing the motion of our friend, the American Kastral. So in this video, we'll be further describing the Kastras motion using numbers and variables. So let's review. This placement is the change in position. We also said that for displacement, we only take the distance of a straight line connecting the two points. For velocity, we said that this is the change in displacement over time. And because velocity is a vector, we said that it has a magnitude and a direction, such as negative or positive direction. And then we talked about acceleration, which is a change in velocity over time. Let's assume the Kastral starts at 1.5 kilometers and flies for a certain amount of distance before stopping at a branch at 10 kilometers. What is its displacement? So this time, pay attention to the x-axis because our Kastral is flying in the x-axis direction. So it's initial position, it's going to be 1.5 kilometers, and it's final position is going to be 10 kilometers. So the change in position will be delta x equals x final minus x initial. Now we can plug the numbers in and we get 8.5 kilometers as its displacement. Remember that when we're talking about displacement, we're not talking about the Kastras entire flight path. We're just talking about the red line as indicated in this drawing. So it's a straight line connecting the points of the initial position and the final position. Now let's talk about velocity. Remember this is the change in displacement over time. Let's say it takes the Kastral 5 seconds to go from position A to position B. And we'll set the initial time to 0 for simplicity. Now you might also know that we have meters instead of kilometers. This is just for simplicity so we don't have to convert to SI units. Now remember that velocity is actually a vector. So we're going to say the Kastral is traveling in the positive direction towards the x-axis. And since velocity is displacement over time, we have this, change in x over the change in time. This is how the formula looks with the numbers. And we get 1.7 meters per second. This is actually kind of slow for a Kastral. So at this point, you should stop and think about whether the numbers actually make sense. The slow Kastral now decides to accelerate to catch its prey. And remember, we said the acceleration is just a change in velocity over time. So let's assume the Kastral gone to shape and it's going 60 kilometers per hour at a constant velocity. Suddenly, it sharply accelerates down to catch its prey. So now, it's far enough velocity is actually 100 kilometers per hour. So for velocity, I was nice and decided to leave the units as meters. But this time we have kilometers per hour. And so we need to convert this to SI units in meters per second. And we get 16.6 meters per second and 27.7 meters per second, which is actually quite normal for a Kastral. So now we have converted the final velocity and the initial velocity into SI units and we can work with the formula. We're going to say that it takes the Kastral for seconds to make this change in velocity. So we're going to set T equals zero for the initial time. This is because when we plug the numbers in, we have nice simple numbers to work with. And we get 2.7 meters over second squared. You might be wondering why it's second squared. Well let's find out. We can see that when we break up the units acceleration is actually distance over time, over time, which gives us distance over time squared. So we get meters over second squared. This is why it's always important to remember the units when working in kinematics. So in the next video, we're going to be trying to visualize the Kastral's motion by working with graphs. See you then.