Question

A square lamina (each side equal to 2m) is submerged vertically in water such that the upper edge of the lamina is at a depth of 0.5 m from the free surface. What will be the total water pressure (in kN) on the lamina?

(a) 19.62

(b) 39.24

(c) 58.86

(d) 78.48

This question was posed to me during a job interview.

My question is taken from Hydrostatic Force on Plane Area in division Hydrostatic Forces on Surfaces of Fluid Mechanics

Answer 1

The correct option is (c) 58.86

Easiest 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 * 10^3 N / m^3; y = 0.5 + ^1 ⁄ 2 * 2m = 1.5 m, A = 2 * 2 m^2 = 4 m^2. Hence, F = 58.86 kN.