1. The problem statement, all variables and given/known data The question asks to find the magnitude of the pressure force on the gate: 3. The attempt at a solution Here is the part of the solution: I don't get why zc is 3.667m. Shouldn't it be 3 + (2/3)sin40 since you want the depth of the centroid from the surface to the gate? Also, another way to solve this would be to find the horizontal force and vertical forces. This would mean that I would have to for the weight of the fluid under the gate in order to find the vertical force right?