Which one is better to describe lift of a plane wing:
Newton's third law of motion:
(The wing applies a force on air and the air applies an equal and opposite force on wing - which causes lift.)
OR
Pressure:
(The force that is created from the higher pressure region to the lower pressure region is what causes lift.)
Basically, which one would be the most optimum in describing the lift force that is generated on the wing by the air?
As an explanation of wing lift, I prefer the downward deflection story. This explanation can be explained with other experiences with fluids. A swimmer propels themselves forward by pushing water backwards. An airplane stays up by pushing air down. If you hold a flattened hand out of a moving car and tilt the leading edge upwards, you can feel the wind hitting the bottom of your hand, pushing it up.
This is not to say that the pressure story is false. The air pressure above the wing is in fact lower than below the wing, but it can be difficult to explain why there is a pressure difference. If you say that air flows over the wing faster than under the wing, this just raises the question of why there is a difference in flow speed. Answering that question is complex.
Both explanations are equivalent (as they should be, since they describe the same phenomenon). Air is deflected downwards and the air pressure is higher beneath the wing.
The first one is correct.
The second one (the way the diagram says it anyway) is incorrect and a very common misconception, or at best misleading and rather thin.
In my mind, it's better to say there exist higher and lower pressure regions BECAUSE of the force of the wings on the air. They are two sides of the same coin, but the wing is causing that pressure condition, not taking advantage of an existing condition.
Recommend watching this short treatment https://youtu.be/aFO4PBolwFg
