Posted on Monday, October 27, 2008 at 11:48:33 AM

The Bernoulli Principle

Airplanes fly when the movement of air across their wings creates an upward force on the wings (and thus the rest of the plane) that is greater than the force of gravity pulling the plane toward the earth.

The physics behind this phenomenon was first described by Daniel Bernoulli, an 18th century Swiss mathematician and scientist who studied the movement of fluids. Bernoulli discovered that the pressure exerted by a moving fluid is inversely proportional to the speed of the fluid. In other words, fluid pressure decreases as fluid speed increases, and vice versa.

The same principle applies to moving air. The faster that air moves through a space, the lower the air pressure; the slower it moves, the higher the pressure. Aircraft wings are designed to take advantage of that fact and create the lift force necessary to overcome the weight of the aircraft, and get airplanes off the ground. The undersides of wings are more or less flat, while their tops are curved. In addition, wings are slanted slightly downward from front to back, so air moving around a wing has a longer way to travel over the top than it does underneath. The air going over the top moves faster than the air going underneath, and the air pressure above the wing thus is lower than it is under the wing, where slower moving air molecules bunch together. The pressure differential creates lift, and the faster the wing moves through the air, the greater the lift becomes, eventually overcoming the force of gravity upon the aircraft. read more...

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