A vertical plate is submerged in water as indicated in the figure.

Observe the figure,

At any instant the depth of the plate from the surface is .

At one end of the plate consider the width as .

From the property of similar triangles,

Strip area of one side of the plate is  , as depth increases then also increases.

.

Hydrostatic pressure, , where is the depth of the vertical plate which is submerged into water.

.

Find the hydrostatic force  on one end of the aquarium:

.

.

Hydrostatic force as a Riemann sum  .

As the depth of the plate is  , then Integral limits are varies from to .

Set up the integral .

Weight density of the water .

.

 Hydrostatic force on one end of the aquarium is .

 Hydrostatic force on one end of the aquarium is .