which means the deer hasĪ way higher acceleration compared to the cheetah. That is 10 meters per second per second, or 10 meters over second squared. And so that would equal 20 divided by two. 20 minus zero divided by two seconds, because it reaches 20 in only two seconds. So the acceleration for ourĭeer is going to be v minus u by the same formula. Again at time zero, ourĭeer's also be zero. What is the acceleration of this deer? Is it more than theĬheetah or less than that? Again, pause the video and We see that even thisĭeer is accelerating. And it's velocity-time graph is over here. Whew! Things are getting very interesting. Okay, now let's say there's a deer that is chasing this cheetah. Every second it's increasing its speed by four meters per second. What does it mean? It means our cheetah is gaining a speed of four meters per second every second. Meters per second per second, Which we call four meters 20 divided by five, that's going to be four And that number equals 20 divide by five. Taken for that change? And the time taken was five seconds. And so acceleration becomes final velocity minus, it's meters per second, minus initial velocity, which is zero. If you can calculate the acceleration by looking at the graph. Go ahead, pause the videoĪnd see if you can do this. In fact, you know what? See if you can try this on yourself first. Change in velocity is always calculated as the final velocity, v We define acceleration, a,Īs the change in velocity divided by time. How do we calculateĪcceleration in general. So, can we calculate this acceleration by looking at this graph? Well, let's see. Okay, now that we know our cheetah is getting faster and faster, it means it's accelerating, right? Whenever objects change their speed, whether they increase it or decrease it, we say that object is accelerating. There is no informationĪbout its position, but only about its speed and direction. It could have been at zero, but it could have been a hundred meters or maybe it would have been So I have no idea where thisĬheetah was to begin with. But it doesn't tell usĪnything about its location, its position. Speed, how fast it's going, and it tells us in whatĭirection is going. Where that object is, or where that vehicle is, right? Similarly, the velocity-time graph, also tells us only the Looking at the speedometer of a vehicle, it only tells us how fast it's going, but it doesn't tell us To think about is that just like when you're So if we attach this speedometer to it, then as time ticks, it getsįaster and faster and faster, and at the end of five seconds, it hits 20 meters per second. Pretty much visualize what our cheetah is doing. And we don't know what happens after that because the graph ends over there. The end of five seconds, it reaches a spirit ofĢ0 meters per second. When we just start our timer it has zero speed, but then it quickly accelerates. So if we had a speedometerĪttached to our cheetah, then it would look somewhat like this. So it's speed is continuously increasing and at the end of five seconds, it has reached 20 meters per second. That at time, t equal to zero, our cheetah has zero speed. So what is the graph saying? Well, the graph is saying Much about the direction, we'll only concentrate on the speed part. It could mean to the left or it could mean downwards, anything. And if the graph were toĬome below the t-axis, then we would say the Here about the time axis, then we can say the object is moving in one particular direction, let's say to the right, or Positive, like right now, like you can see over How does this graph give us a direction? Well, if the graph is The only difference is, here, it not only gives us the speed, not only tells us how fast it's going, but it also tells us in what direction that object is moving. The speed of our vehicle is at every moments in time. The velocity of any object, like our cheetah, atĮvery moments in time. So, what's a velocity-time graph? It's a graph that tells us Whew, So let's see if weĬan analyze this graph and visualize what our cheetah is doing. But since you like physics so much, instead of showing you the clip, I give you it's a velocity-time graph. A cheetah is running somewhere and you would love to see it.
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