How can airplans fly?

Answer 1

The simple answer is that they use an airfoil. How the airfoil works is the complicated answer. You know about air pressure, right? It's constantly pushing on everything from every direction. An airfoil changes that. The top, or cambered, side has a hump on top of it, for lack of a better term. The bottom side is just flat. If you were to measure the distance from the leading edge (front) to the trailing edge (back) on the top and bottom, you'd notice that the distance on top is longer than on the bottom. This is key. When an airplane moves, air rushes over the wing on both sides. However, the air going over the top must go faster to keep up with the air on the bottom because the distance over the top is longer. If the top was flat like the bottom, then the air pressure would be the same on both sides. But because the air on top has to move faster than on the bottom, it can't stay and push down on the wing as long. This results in lower air pressure on top than on the bottom. The faster the plane goes, then the stronger this effect is. At 50 m.p.h., the effect is not strong enough to lift the plane unless it's a very, VERY light plane. At 180 m.p.h. (standard takeoff speed), the effect is so great that is able to counter the effects of gravity and the plane will leave the ground. So the entire source of lift is from air on the bottom pushing up harder than the air on the top. To see this effect at home, take a strip of paper, hold one end close to your mouth, and blow across the top. The same principle is at work, only on a much smaller scale. I hope that this explanation was easy to understand. If not, then I'm very sorry, but I can't think of a simpler yet accurate way to say this.