Torricelli's law
Torricelli's law, also known as Torricelli's theorem, is a theorem in fluid dynamics relating the speed of fluid flowing from a hole to the height of fluid above the hole. The law states that the speed v {\displaystyle v} of efflux of a fluid through a sharp-edged hole in the wall of the tank filled to a height h {\displaystyle h} above the hole is the same as the speed that a body would acquire in falling freely from a height h {\displaystyle h} , v = 2 g h {\displaystyle v={\sqrt {2gh}}} where g {\displaystyle g} is the acceleration due to gravity.