A cubical box is completely filled with water. Prove that the total thrust exerted by water on one of the vertical walls is equal to half the weight of water kept in the box.

Explanation

Let each side of the cubical box be of length x.
Mass of water kept in the box, `m=x^(3)xx1=x^(3)`
`therefore` Thrust exerted by water on any one of the vertical walls
= lateral pressure `xx` area
= `x/2xx1xxgxx x^(2)=1/2x^(3)g=1/2mg`
= `1/2xx` weight of water kept in the box.