 Torricelli's law

An ideal fluid issuing from a small hole a vertical depth $h$ below a free surface has speed

Torricelli's law is a principle in fluid dynamics that describes the speed of fluid flowing out of an orifice under the influence of gravity. It states that the speed (velocity) \( v \) of a fluid flowing out of an opening at the bottom of a tank is proportional to the square root of the height \( h \) of the fluid above the opening.