Newton's laws and Bernoulli's Principle create lift

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How lift is created - Bernoulli's Principle:

In some textbooks and general references, Bernoulli's Principle is the sole explanation of lift. However, this explanation is incomplete. Newton's Laws must also be considered. For instance, the effect of camber creates lower pressure and it forces air down. According to Newton's 3rd Law, the reaction of the air being pushed down is that the wing is pushed up.

Bernoulli's Principle, although never considered by the Wright brothers, helps to explain the camber and efficiency.

 

"Bernoulli's Principle" states that when the velocity of a fluid is faster, the pressure of the fluid is lower. In contrast, this means that slower moving fluids have higher pressure.

 

Bernoulli's principle applies to flight in the following manner: Air passes faster over the top of a cambered wing and therefore results in lower pressure. See the diagram below. As you can see, the top of the wing is curved. The air that passes over the top of the wing moves faster because it travels a greater distance in the same amount of time as compared to the air that passes under the wing. Lift is created because the air under the wing is slower and exerts higher air pressure. The differences in pressure create lift.

Speed of the air matters! This is why birds and planes take off into the wind! Imagine a plane sitting on a runway during a hurricane. Imagine the wind blowing over the wings from the nose to the tail. How would you expect the plane to behave? (Assume that the wind will not blow the plane end over end.) Answer: The plane would rise!

How lift is created - Newton's Laws

Newton's 2nd law (F = ma)

If the plane accelerates, Newton’s 2nd Law (F = ma) can be used to understand its motion. For instance, Newton's 2nd law can explain the relationship between the force of the air on the plane, the mass of the plane and the acceleration of a plane.

 

More information concerning F = ma

Newton's 3rd law (F = -F)

If a plane flies at constant speed, it stays in the air due to Newton's 3rd law. The direct pressure of the air pushing on the bottom of the wing keeps the plane in the air. In other words, as the wing pushes down on the air, the air pushes up with an equal and opposite force. Newton's 3rd law states that forces always come in equal and opposite pairs. For instance, if you push on a wall, the wall pushes back with the same amount of force. Newton's 3rd law always governs during the flight of a plane.

See more information on action-reaction pairs.

See more information on Law 3: Action/Reaction

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