0:00
All right, hello.
00:01
In this question, we've given this up.
00:02
We have a block that we're carrying along a horizontal plane.
00:06
And we're applying a force at some angle theta.
00:09
So it's not totally in the horizontal direction.
00:11
And we're told that there is a coefficient of friction on here.
00:15
So if i draw another force on here, friction always opposes the motion of an object.
00:20
So if i'm pulling this to the right overall, then i'm going to have a frictional force going to the left.
00:25
And then my last force is i'm going to have some normal force that the ground is exerting on the box.
00:30
If i want to go ahead and write a sum of the forces for this, in the y direction, while i have my normal force pushing up, i also have a component of my y force pushing up.
00:39
I have this fay here.
00:42
And that's going to be fa times the sine of theta, because it's the opposite side.
00:47
Those are the upward forces.
00:48
And then i have weight pulling it down.
00:50
That's going to equal 0, because in the y direction, in the up and down direction, i don't have any acceleration.
00:56
It's not jumping up or jumping down.
00:57
So this is going to equal 0.
00:59
So that's my sum of the forces in the y direction.
01:01
My sum of the forces in the x direction, well, i have my applied force, but just the x component here, which is the cosine of theta component of my applied force, going in one direction.
01:11
And then i have my force of friction opposing that.
01:13
And that's going to equal my mass times the acceleration.
01:17
If i want to go ahead and expand this out, i'm going to have my applied force times the cosine of theta minus.
01:21
I know that my force of friction is mu times my normal force.
01:24
Well, what is my normal force? it's going to be my weight minus my applied force in the y direction...