Hydro Static Pressure

Fluid force is constant at any particular depth but varies vertically. This force is calculated as liquid weight per unit volume times the depth. The total force exerted by the liquid on the ring section is non-uniformly applied vertically. When the quadrant is immersed in water it is possible to analyze the forces acting on the surfaces of the quadrant as follows:

The hydro static force at any point on the curved surface is normal to the surface and therefore resolves through the pivot point because this is located at the origin of the radii. Hydro static forces on the upper and lower curved surfaces therefore have no net effect – no torque to affect the equilibrium of the assembly because all of these forces pass through the pivot.

The forces on the sides of the quadrant are horizontal and cancel out (equal and opposite). The hydro static force on the vertical submerged face is counteracted by the balanced weight W. The resultant hydro static force on the face can therefore be calculated from the value of the balance weight and the depth of the water