Bernoulli’s theorem

Principle that relates pressure, velocity, and height for a non viscous fluid with steady flow. A consequence is that, for horizontal flow, as the speed of a fluid increases, the pressure it exerts decreases. Derived by Daniel Bernoulli  the principle explains the lift of an airplane in motion. As the speed of the plane increases, air flows faster over the curved top of the wing than underneath. The upward pressure exerted by the air under the wing is thus greater than the pressure exerted downward above the wing, resulting in a net upward force, or lift. Race cars use the principle to keep their wheels pressed to the ground as they accelerate. A race car’s spoiler—shaped like an upside-down wing, with the curved surface at the bottom—produces a net downward force.

Bernoulli’s theorem states that the total energy of a small amount of an incompressible liquid flowing from one point to another without friction remains constant throughout the displacement.

 ie; pressure energy + potential energy + kinetic energy =constant.

when unit mass of liquid flows through a tube ,

p/ρ +1/2V^{2     +hg =constant.}

p =pressure, ρ =density, v= velocity of flow,h = pressure head

link :http://www.way2science.com/bernoullis-theorem/