define the pressure on a vertical planefluid

Question

Define the Pressure on a vertical plane

Fluid pressure increases linearly with increasing depth. The average pressure on a vertical plane occurs at the average vertical depth. This is measured from the fluid surface to the top of the vertical plane (h₁), and from the fluid surface to the bottom of the vertical plane (h₂).

Average Ρ = ½ (γ) (h₁+h₂)