00:01
So in this problem, we have a block with a mass of 0 .35 kilograms.
00:06
The block is on a horizontal surface.
00:09
That surface has coefficients of static and kinetic friction listed here, 0 .61 and 0 .47 respectively.
00:18
And then there is an external force p applied at an angle of 40 degrees.
00:23
We want to find the maximum magnitude of the force p applied in newton's before the block starts to move.
00:32
So to do that, we're going to start with the sum of the forces in each of our directions here.
00:39
So in the y direction, we know the block isn't going to move up and down.
00:44
So we have, from our force diagram over here, we have the normal force, which is acting in the positive y direction.
00:52
We have the weight, which is acting in the negative y direction.
00:55
So i've applied a negative sign here.
00:57
And we have the y component of our force.
01:01
P and all of these need to be equal to zero because we're not going to move up or down.
01:08
And we have the sum of the forces in the x direction has to be equal to in the positive x direction here we have px minus the force due to friction here because it's resisting our pushing force p and all of those have to be equal to zero because we're considering a situation in which the block is just about to move.
01:39
We're just about to overcome our static coefficient of friction here.
01:45
So the acceleration in the x direction should still be zero...