I'm really stuck on these two problems: 1) Two equal uniform rods AB BC are smoothly jointed in B and they're in equilibrium. The end of C lies on a rough horizontal plane and the end of A is freely pivoted at a point above the plane. If alpha and beta are the angles of CB and BA with the horizontal, prove that mu > 2/[tan(beta)+3tan(alpha)] 2)A uniform sphere of radius r and weight W has a ligjht inextensible string attached to a point on its surface, while the other end is attached to a rough vertical wall. The sphere is in equilibrium touching the wall at a distance h below the point of attachment to the wall and is about to slip. a)If coefficient of friction=mu find the angle of the string with the vertical b)If mu=h/2r show that the tension in the string is W[Sqrt(1+mu^2)]/2mu I've tried every combination of forces that came in my mind, with no result. Of course I've balanced, taken the moments, etc.. Can someone help me? Thanks!