There's a lot of mis-information about how lift is produced, but some parts of the traditional explaination are true:
- Pressure does drop when a fluid is flowing faster.
- If there is a pressure differential between two sides of an object, it will feel a force.
The essential thing to know about lift is that a wing usually flies at a slight angle (know as the 'angle of attack' and given the greek symbol 'alpha' in equations). The leading edge is higher than the trailing edge. Think of a surfer: the nose of the board is higher than the surface of the wave, and the tail is just below the surface and as the board moves forward it is constantly climbing out of the 'hole' in the water that it would sink into if it stopped.
A surfboard isn't a perfect analogy but you can see how an angled wing will develop a high pressure on the underside, and a lower pressure on the top. This pressure differential deflects air downwards.
The curved shape of a wing helps to deflect the air gradually, and reduce drag, but it's not essential. A flat plate works well enough for light models, and aerobatic planes can fly upside down without changing the their aerofoils.
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