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## Homework Statement

Here is a horrible diagram representing the problem:

The problem is to find the minimum coefficient of static friction between the ball and the wall so that the ball remains motionless.

## Homework Equations

torque = r*F

## The Attempt at a Solution

I've divided the tension force into x and y components, Tsinθ and Tcosθ respectively. Therefore the normal force (the wall pushing against the ball) is N = Tsinθ. The friction force is = uN = u(Tsinθ).

So now, because the ball is motionless, the two torques must cancel each other out. So Torque from the tension T(t) = (radius)*T and torque from the friction force T(f) = radius*Friction force = radius* uTsinθ. This gives u = (1/sinθ)... but I'm really not sure... also, how do I minimize this u?

Thanks in advance for any help.