This is not a HW question!!! THIS IS A DISCOVERY that I want to explore. I will explain it as follows: Suppose I have this exercise, where I know the static coeffecient between the beam and the floor is 0.3, whereas in the wall there is no friction. I want to find out if the beam slides, or stays up. That's easy. http://img703.imageshack.us/img703/4676/fsmaxtest.jpg [Broken] So by doing the calculations, I can see the beam doesn't slide. I solved the problem. Now, let's say I want to experiment further. What happens if I put the result of Fs I got when I didn't calculate Fs_max into the Fs = N x μ equation? I think it's a valid thing to do, since it's in the formula. But what happens then? I'd get a different result for N. Which doesn't make sense, since N must be 30 [N] to resist the weight of the beam. The friction coefficient sure can't change, since it is constant! So, what did I just do? Did I find loop in mechanics theory?