00:01
Hello there.
00:03
In this video, the concept we're going to be looking at is power.
00:11
Okay, now suppose we have a car going up a hill, and let's write down what we know.
00:21
Suppose the mass is 1 ,300 kilograms.
00:29
Let's say the car starts from rest.
00:32
So we have a v -0 of zero meters per second.
00:35
Let's say it gets up to 30 meters per second.
00:41
And let's say it takes 12 seconds to do that.
00:48
And let's say the incline is 15 degrees.
00:54
And we need to find the power.
00:57
Okay.
00:58
So if we look at the force diagram, so a free body diagram, let's say our hill is going like this.
01:10
Okay.
01:12
And so let's say our car is there.
01:14
We've got the force of the car that's taking it up the hill.
01:22
And then we've got the weight of the car.
01:27
There's our incline.
01:30
Okay.
01:31
If we draw a perpendicular here and then go back.
01:37
So that's theta.
01:38
This is also theta up here.
01:43
Okay.
01:44
And so if we say the x component, is positive up, then we only need to worry about the forces in the x direction.
01:56
There's also a normal force of the car on the hill, but we can leave that out for now.
02:03
So we want to sum the forces in the x direction, and that will be the mass times the acceleration in the x direction.
02:14
We also have zero acceleration in the y direction, so our our x component of acceleration will be the acceleration.
02:24
All right.
02:25
So we have an f going up and going down.
02:31
We have minus the y, sorry, the x component of weight.
02:39
So if we do the sign of theta, we get wy over w.
02:45
So we have f minus w sine theta is ma.
02:54
W is mg.
02:57
So we have mg sine theta plus ma.
03:02
We can factor out the m.
03:06
G sine theta plus a.
03:10
Okay, so we're going to need that acceleration.
03:13
Well, acceleration is the change in velocity over time.
03:19
Okay, so our acceleration is the 30 meters per second minus zero meters per second over the 12 seconds...