1. The problem statement, all variables and given/known data Find the mass necessary for equilibrium to occur in the following image. Assume that the mass and the friction of the pulleys are negligible. 2. Relevant equations None directly provided for this problem. 3. The attempt at a solution I figured for this problem I would set the sum of the net torques on the pulley equal to zero, because then the pulley is not spinning and the system is in equilibrium. Here is my equation: gravity = 9.8 m/s Since torque is the cross product of the force times the perpendicular distance from the axis of rotation, I used counterclockwise torque (provided by the truck) = F*rsin(x), but since the force is already perpendicular to the axis of rotation in the image I just used F*r, where the F = 1500*9.8*sin(45). The clockwise torque on the pulley is m*g*3r ƩT = 1500kg*9.8*sin(45)*r - m*g*3r = 0 add m*g*3r to both sides and then divide by r to obtain: ƩT = 1500kg*9.8*sin(45) = m*g*3 solving for the mass I get 353 kg, but the answer is 178 kg. I noticed that multipying the right side by 6 instead of 3 yields the right answer, I just don't know why or what I'm doing wrong.