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.

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

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Find the hydrostatic force  on one end of the vertical plate:

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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 .

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 Hydrostatic force  on one end of the aquarium is .

 Hydrostatic force  on one end of the aquarium is .