A uniform ladder of a length 5m and a mass 15 kg leans against a wall, making a 45 degree angle with the ground. The wall is capable of supporting a maximum of 500 N. A fireman must climb the ladder to it's midpoint, what is the max mass that the fireman can be without collapsing the wall. Ok...So I know that for a uniform problem we know that this means that the Center of Mass will be halfway along the lengh of the board. Again since this is a center of mass problem the sum of the torques must equal zero. Et=0 I assumed that I would need to take the (max force)(cos 45) + (Weight of ladder)(distance of ladder) then divide that by the (total distance of the ladder) The answer should be 86.95kg But I got.. (500N)cos45 + (15kg)(5m) = 353.33N + 75 kg.m = 428.33 N.kg.m / 5.0m = 85.66 = 86 kg I am doing something wrong. I am not able to cancel out some of my units. Its seems like a simple mistake but any advice would help!! Thanks!