Not to be confused with Torricelli's equation or Torricelli point.
Torricelli's law, also known as Torricelli's theorem, is a theorem in fluid dynamics relating the speed of fluid flowing out of an opening to the height of fluid above the opening.
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Torricelli's law states that the speed of efflux, v, of a fluid through a sharp-edged hole at the bottom of a tank filled to a depth h is the same as the speed that a body (in this case a drop of water) would acquire in falling freely from a height h, i.e. v = sqrt{2gh}, where g is the acceleration due to gravity (9.81 N/kg). This last expression comes from equating the kinetic energy gained, frac{1}{2}mv^2, with the potential energy lost, mgh , and solving for v.
The law was discovered (though not in this form) by the Italian scientist Evangelista Torricelli, in 1643. It was later shown to be a particular case of Bernoulli's principle.