Bernoulli's principle states that in fluid flow, an increase in velocity occurs simultaneously with decrease in pressure. It is named for the Dutch/Swiss mathematician/scientist Daniel Bernoulli, though it was previously understood by Leonhard Euler and others. For a mathematical formulation, see Bernoulli's equation. In a fluid flow with no viscosity, and therefore one in which a pressure difference is the only accelerating force, it is equivalent to Newton's laws of motion.
Bernoulli's principle is also important in carburetors. In a carburetor, air is passed through a Venturi tube to increase its speed and therefore decrease its pressure. The low pressure air is routed over a tube leading to a fuel tank. The low pressure sucks the fuel into the airflow so that the combined fuel and air can be sent to the engine. This same effect can be observed by blowing over a straw; the liquid level will rise as the flow over the top of the straw increases in speed.
Source: Wikipedia
