The relationship between the velocity and pressure
exerted by a moving liquid is described by the Bernoulli's
principle: as the velocity of a fluid increases, the pressure
exerted by that fluid decreases.
Airplanes get a part of their lift by taking advantage
of Bernoulli's principle. Race cars employ Bernoulli's principle
to keep their rear wheels on the ground while traveling at high speeds.
The Continuity Equation relates the speed of a fluid moving through a pipe
to the cross sectional area of the pipe. It says that as a radius of the
pipe decreases the speed of fluid flow must increase and visa-versa.
This interactive tool lets you explore this principle of fluids.
You can change the diameter of the red section of the pipe by dragging
the top red edge up or down.