1. The problem statement, all variables and given/known data The 4000N concrete pipe is being lowered from the truck bed when it is in the position shown: If the coefficient of static friction at the points of support A and B is 0.4, determine where it begins to slip first: at A or B or both at A and B 2. Relevant equations It's not so complicated task. ΣFx = 0 = Na+Fb - Wsinθ ΣFy = 0 = Nb+Fa - Wcosθ ΣMo = 0 = Fbr - Far = 0 Fmax=μNmax 3. The attempt at a solution The question I have is why the friction at support A have the direction with montion of the pipe and not trying to oppose the motion. We assume that the pipe is moving clockwise direction according to our friction direction at support B. Can someone explain me this ?