00:01
So in this problem, we are given the relation of the velocity of the car versus time.
00:09
So in part a, i want to describe what happened to the car at time t equal to zero.
00:14
So as we can see that at t equal zero, yeah, at t equal to zero, we see that the velocity begin decreasing, right? so at t equal to zero, so the car start decelerating.
00:32
Okay.
00:39
So cars start accelerating at t equal 1.
00:42
And part b, how does the car average velocity between 2 equal 0 to t equal 1 compared to the average velocity between t equal 1 and equal 5? so from t equal, so part b, from t equals 0 to t equal 1, we can easily see that the average velocity is over here, right? so it's 10 meters per second.
01:06
V bar is 10 meters per second from 0 to 1.
01:11
And from 1 to 5, so again, we see that it's right here, right? it's just the middle of the highest position, lowest position, which is over here.
01:21
So it's also 10.
01:23
V bar equal 10 meters per second.
01:26
So this is from 1 to 5.
01:27
So in that sense, the average velocity of these two intervals are the same.
01:34
And part c says that what is the displacement of the car from 0 to 0.
01:39
To 7.
01:43
So because we basically have three stages, the first stage is from 0 to 1, right? so the displacement from 0 to 1, let's say it's x01 equal half.
01:57
So t is from 0 to 1, right? so it's 1.
02:00
And times the, so basically we're just calculating the area of this triangle, all right? so times 20.
02:11
So this gives you 10 meters.
02:13
And then the second stage is from 1 to 5.
02:16
So we need to calculate the area of this triangle.
02:21
X15 equal half times so 5 minus 1 and times 20.
02:30
So this gives you 40 meters.
02:36
And then it's from 5 to 7.
02:41
We need to calculate this area.
02:46
So x 5 to 7 equal, because as you can see that the velocity is negative in this area, right? so the area here is also negative.
02:55
So it equals half, negative half, and the time is from 5 to 7, 7 minus 5, and times 20...