Gravity and Lift

Gravity

Gravity is the only reason paper airplanes don’t fly forever. If gravity’s downward force wasn’t acting on the plane, it would have no reason to descend. However, gravity is counteracted by the plane's lift.

 

Lift

For “real” airplanes, lift is typically explained with a diagram of the wing, displaying how the curve on top the wing forces air to travel quickly over it, while the air below it travels more slowly. This cause a difference in pressure, and this pressure is what lifts the plane up. (2)


http://ambitiontofly.files.wordpress.com/2011/10/wings_flow_air2.gif

However, paper airplanes clearly don’t have this same feature, so where do they get their lift?

Well, the principle is still the same, but the method is different. Paper airplane wings are angled so as the body travels forward, the air has to spend more time rushing over it. In fact, try building a plane so the wings angle downward sharply toward the nose and up toward the back. When you throw this plane (at any somewhat horizontal angle), it should have so much lift that it will immediately shoot straight up and fall to the ground. A paper plane does not have very much weight to it, so the wing/body ratio and the amount of lift generated are very important to moderate. Too much lift can easily throw the plane out of stability. (4)