1. The problem statement, all variables and given/known data A ladder on the rough floor is leaning against a vertical rough wall. The ladder has length l and mass m. The coefficients of friction are μ for both contact surfaces. What is the smallest angle between the ladder and the floor? 2. Relevant equations ∑F=ma ∑τ = F⊥ r fs ≤ μsN 3. The attempt at a solution ∑Fy = 0 N2 + f1 - W = 0 ∑Fx = 0 f2 - N1 = 0 f2 = N1 ∑τ about the ground = 0 N1lsinθ + f1lcosθ - W(l/2)(cosθ) = 0 For θ to be the smallest angle, what is the condition? Is it f1 = μN1 or f2 = μN2 or both of them need to happen at the same time?