00:01
So in this question, we have a fan that was just turned off, and its angular velocity is decreasing from an initial angular velocity of 500 revolutions per minute, which we will convert to revolutions per second.
00:20
So we're going to do that, you know that one minute, that's 60 seconds.
00:29
And so this is going to give me 8 .33 reds per second.
00:37
And our final velocity is 200 revs per minute.
00:48
And again, same conversion, which is going to be 3 .33 revs per second.
01:00
And we know that this all happens in a time for seconds.
01:08
And we want to know first, what is the angular acceleration in revolutions per second square? so since they want revolutions per second square, right now we have the proper units.
01:18
We normally would convert these to radians per second, but we don't need that here because it's asking for revolutions per second square.
01:25
So the way that we're going to do this, this is a kinematic question.
01:29
So it's kind of like the kinematic equations for linear.
01:32
So we have final omega, initial omega, and t.
01:36
So we're going to use omega -equals omega -not plus alpha -t.
01:44
Again, i'm going to leave out units just for room's sake right now.
01:47
8 .33 equals 3 .33.
01:51
Turn it backwards, plus alpha times four seconds.
02:13
Okay, so we subtract our 8 .33 both sides, get negative 5, divided by 4, and we get an acceleration of negative 1 .25 revolutions per second square...