00:01
So here, for part a, we have that theta is equaling 60 degrees, and we can apply newton's second law to the downhill direction where we say mg sine of theta, minus the frictional force is going to be equalling the mass times the acceleration.
00:16
And so we can say the frictional force is equalling the kinetic frictional force, which would give us the coefficient of kinetic friction multiplied by the normal force.
00:24
And this is going to give us the coefficient of kinetic friction times mg cosine of theta after applying newton's force.
00:30
Second law in the y direction or perpendicular to the incline and so we can say that then for part a the acceleration is going to be equaling to g multiplied by sine of theta minus the coefficient of kinetic friction multiplied by cosine of theta and so here with the coefficient of kinetic friction being 0 .20 we can say that the acceleration is equaling 9 .8 meters per second squared multiplied by sine of 60 degrees minus 0 .20 multiplied by cosine of 60 degrees and we find that the acceleration is equaling 7 .5 meters per second squared.
01:19
So that'd be for part a.
01:20
For part b we know that the acceleration is directed down the incline or down the slope.
01:37
And for part c now the friction force is in the downhill direction, which is essentially our positive direction.
01:45
So we don't really need to do all the analysis all over again...