Torricelli's law

Torricelli's law states that an ideal fluid exits a small opening at speed √(2gh), matching the speed gained by free fall through height h.

Bernoulli's principle: A relation among pressure, speed, and elevation in steady ideal fluid flow. Applying it between the fluid surface and opening yields Torricelli's speed.
Evangelista Torricelli: An Italian physicist and mathematician who succeeded Galileo as court mathematician in Florence. The law bears his name and grew from his work on fluid pressure and motion.
Discharge coefficient: The ratio of actual flow rate through an opening to its ideal theoretical flow rate. It corrects Torricelli's ideal prediction for contraction and energy losses.
Viscosity: A fluid's resistance to deformation and internal shear flow. Viscosity dissipates energy and makes actual discharge slower than the ideal speed.
Conservation of energy: The principle that energy is transferred or transformed but not created or destroyed in an isolated system. The law equates lost gravitational potential energy with gained kinetic energy.
Galileo Galilei: An Italian astronomer and physicist whose studies included falling bodies and mechanics. Torricelli extended ideas from Galileo's mechanics to the speed of draining fluid.
Orifice plate: A thin plate with a calibrated opening used to measure flow from pressure differences. Its discharge calculations use the ideal orifice-flow relation as a baseline.
Reynolds number: A dimensionless ratio comparing inertial and viscous effects in fluid flow. It helps determine whether flow near an opening is laminar or turbulent.
Hydrostatic pressure: The pressure exerted by a fluid at rest under gravity, increasing with depth. The pressure difference between the surface and opening drives the outflow.
Barometer: An instrument that measures atmospheric pressure. Torricelli's mercury-tube experiment established atmospheric pressure as a measurable cause.

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TorrBroader topic: The law shares Torricelli’s name but concerns fluid flow, not the pressure unit’s definition.