Question

What will be the total pressure (in kN) on a vertical square lamina submerged in a tank of oil (S=0.9) as shown in the figure?

(a) 26.5

(b) 35.3

(c) 44.1

(d) 61.7

This question was posed to me in an international level competition.

The doubt is from Hydrostatic Force on Plane Area in portion Hydrostatic Forces on Surfaces of Fluid Mechanics

Answer 1

The correct choice is (c) 44.1

Explanation: Total liquid pressure on the lamina = F = γyA, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 0.9 * 10^3 N / m^3; y = 2.5m, A = ^1 ⁄ 2 * 2^2 = 2 m^2. Hence, F = 44.1 kN.