State Torricelli's law.

(N/A) Torricelli's law states that the speed of efflux,$v$,of a fluid through an orifice at a depth $h$ below the free surface of the liquid is equal to the speed that a body would acquire in falling freely from rest through a vertical distance $h$.
The mathematical expression for the speed of efflux is given by $v = \sqrt{2gh}$,where $g$ is the acceleration due to gravity and $h$ is the height of the liquid column above the orifice.