A: Money
So much of flying is speed control. I think having a clear understanding of aerodynamics is a basis for that speed control. Understanding the relationship between airspeed and aerodynamics will determine if you are flying the plane or the plane is flying you.
There are two laws of nature that are used to describe what makes a wing fly.
1-Bernoulli's principal says that the speed of a moving fluid increases , the pressure withing the fluid decreases. Making the air speed up over the wing, will cause the pressure of the air over the wing to drop. The higher-pressure air below the wing will then "push" the airplane up.
http://virtualskies.arc.nasa.gov/aeronautics/tutorial/wings.html
for further explanation click the above
2-Newton's Third Law of Nature says that for every action there is an equal and opposite reaction air hits the wing it is deflected and also pushes the wing up and back.
Have you ever felt a sideways tug on your car when it passes a large truck going the opposite direction? that tug is caused by air pressure (Bernoulli), as the car and truck pass each other, they form a narrower space that forces air to speed up. Air pressure drops between the car and truck. The higher air pressure on the other side of the car pushes the car and truck toward each other as they pass.
Another way to think of how Bernoulli is applied to aviation via a real life example is when you take a shower, if you have a shower curtain and the water is running it comes towards you just a little. Again the water (air) is moving faster and the pressure is less inside the tub area and the curtain (wing) is pushed in.
Newton's law is illustrated when you are moving in a car and stick you arm out with your hand (wing) flat against the uncoming wind. Your hand is pushed up and back as you increase the angle of you hand with the wind.
