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August 24, 2005



The wings of airplanes and sails of sailing boats are based on the same two scientific principles. One is Newton's third law which is called the law of Action and Reaction, and the other is Bernoulli's Principle. The former is easy to understand because it seems very natural that a wing or a sail is blown in the same direction as the wind. It was so natural that it had been unconsciously used long before Newton discovered it. This old style of sailing a boat is one of the examples; it can sail only in the same direction as the wind and the crew have to row it if they want to sail against the wind. The latter one, Bernoulli's principle, is related to the airflow, that is to say the air separated at the head of the wing meeting the air at the tail of the wing, causing a different air pressure which creates lift. All airplanes and modern sailing boats use this principle effectively so that they can fly or sail against the wind. Flying and sailing have a lot in common.

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