00:01
So here the best figure to use would be figure 6 -4 in the textbook.
00:05
This figure essentially is a very similar system, and we can use the same coordinate system as that figure.
00:12
So for part a, to apply newton's second law in the x and y directions, for the x direction, we have t cosine of phi minus the frictional force f minus the mass times the acceleration.
00:22
In the y direction, we have t sine of theta plus the normal force minus mg.
00:28
This is going to be equaling to zero.
00:30
And we can set the acceleration equaling to zero, and the frictional force equaling the maximum static frictional force, which would be equaling to the coefficient of static friction, multiplied by the force normal.
00:42
We know that then the force normal is going to be equalling to mg minus t sine of theta.
00:49
Solving then for the mass m, we have the mass equaling t over g multiplied by sine of phi plus cosine of phi, divided by the coefficient of static friction...