00:01
So here we have a fan.
00:02
The initial, the initial angular velocity of the fan is going to be 500 rpm, so revolutions per minute.
00:15
And then the final velocity is going to be 200 rpm.
00:21
And then delta t, this occurs in 4 .00 seconds.
00:27
So they want us to find the angular acceleration and the final displacement.
00:35
So we can say angular acceleration equals omega final minus omega initial over delta t.
00:43
This is going to be equal to, we can say, 200.
00:48
This is going to be on rpm.
00:50
So we have to convert it and say one minute over 60 seconds.
00:59
And then we can say minus 500 rpm.
01:08
Again, one minute over 60 seconds.
01:25
And at this point, we can divide the entire thing by four seconds.
01:32
This is going to give us negative 1 .25 revolutions per second squared.
01:40
And then at this point, we can find the angular displacement by saying that angular displacement is equal to initial angular displacement plus initial angular velocity times t plus half alpha t squared.
01:59
And we can actually cancel this out because the initial angular displacement is zero...