Determine the average pressure force acting on the wall of the aquarium 25 cm long and 20 cm

Determine the average pressure force acting on the wall of the aquarium 25 cm long and 20 cm high if it is completely filled with water.

Let’s give the data to us in the SI system:
l = 25 cm = 0.25 m
h = 20 cm = 0.2 m
Water pressure linearly depends on pressure: at the surface level it is equal to zero, at the level of the aquarium bottom – the value of ρgh (Pascal’s law). Therefore, the average pressure on the wall of the aquarium can be found as follows:
Pst = (P0 + Pgl) / 2 = Pgl / 2 = ρ * g * h / 2
The force with which the water presses on the wall:
F = Pst * S, where S = l * h
Let’s substitute everything in the formula for determining the force:
F = (ρ * g * h / 2) * l * h = ρ * g * h² * l / 2
Substitute the numerical values:
F = 1000 * 9.8 * 0.2² * 0.25 / 2 = 49 N
Answer: the force acting on the wall is 49 N.