This is a picture of a quarter cylinder dam gate with a hinge at A and a stopper at B. [Broken] I need to find the force on the stopper at B as a function of the radius (R) and height of the water (h). I was going to do this by working out the moments around the hinge at A. I can solve for pressure forces and weight forces of the gate but I don't know the normal force from the ground. The hinge will have a force in the y direction so it will affect the normal force. I also don't know where to position my normal force, is it always going to be 1/2 of R or will it go through the combined centre of mass of gate and water above?