And, in this case, the friction force

to prevent it sliding down must be in this direction.

And the maximum value of the friction force

is the coefficient of static friction multiplied by the normal force.

So, here is the, the friction force is equal to mu S times N.

And to find the normal force for equilibrium,

we'll just take the components of the forces perpendicular to here.

So I'll just rotate the coordinate system x and

y to be parallel and perpendicular to the show, the slope.

So, summing the forces in the y direction, in other words, this direction,

we have N is equal to the weight of the block times cosine 20 degrees.

And the weight of the block is mg cosine 20.

Or 100 times 9.81 times cosine 20.

In other words, the normal force, at the contact is 922 Newtons.

Next, I sum the forces in the x direction.

In other words, this way.

And here, the forces we have are the friction force, maximum friction force

which I'll call f max, minus the component of the weight force down the slope,

which is W sine 20 degrees plus the tension force in the cable, T.