1. The problem statement, all variables and given/known data A 75kg climber is supported in a "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are .8 and .6, respectively. what is the minimum normal force he must exert? Assume the walls are verticle and that friction forces are both a maximum. 2. Relevant equations F=ma 3. The attempt at a solution This one confuses me. If the climber is to stay in place, its the lower static friction coefficient that matters, isn't it? That being the case, in order to stay in place acceleration must be zero so Ff + Fmg = 0? Working that out though gives .6Fn + 75*9.8 = 0, which comes out to 735, which seems too high. I have to assume I am completly missing something, can someone point me in the right direction?