Hello, Could somebody help me finding the relation between the horizontal force, the weight acting vertically, and the slopes Angle (same for both) that correspond to static equilibrium of the blue ball ? In a first step, I'd like to study this problem without considering friction at all. And in a second step with friction between the ball and the 2 planes only (but maybe there won't be any difference in the result because of the 2 same planes angles ?) I think I need to draw a square triangle using the forces but don't know how to start Any kind of help would be much appreciated! Maybe I should start with a more simple system ? (no friction at the arrow contact) I'm seeking for the horizontal force that ensure equilibrium.