Stating that the speed of the liquid is the same as that of an object in free fall through a height, this describes what theorem of fluid dynamics named, FTP,  for an Italian mathematician who once assisted Galileo?
Consider an open barrel, full of an incompressible fluid.  If you place a spigot in the barrel's side, the fluid will flow out of the hole with a velocity equal to the square root of 2*g*h, where g is the acceleration due to gravity and h is the height between the spigot and the top of the liquid.  Stating that the speed of the liquid is the same as that of an object in free fall through a height, this describes what theorem of fluid dynamics named, FTP,  for an Italian mathematician who once assisted Galileo?
Consider an open barrel, full of an incompressible fluid.  If you place a spigot in the barrel's side, the fluid will flow out of the hole with a velocity equal to the square root of 2*g*h, where g is the acceleration due to gravity and h is the height between the spigot and the top of the liquid.  
Torricelli's Theorem (or Torricelli's Principle)