Explaining How an Airplane Could Take Off From a Giant Conveyor Belt

If an airplane were placed on a giant conveyor belt, with the belt set to move at the exact takeoff speed of the airplane, would the airplane be able to take off? This question's been the source of countless heated arguments online. Although Mythbusters did test this out (by the way, the plane did take off), I'm going to explain how it happened, for those who didn't see the episode or didn't understand the physics behind it. Hopefully this will help to solve the debate.

The treadmill advocates (those who think the plane won't take off) think that because they believe that the treadmill would eliminate any forward motion. They're right in that forward motion is required for enough air to flow over the wings to give enough lift. They're right in that the treadmill's backward motion counter any forward motion the wheels make. Were this experiment being done with a car, yes, the vehicle would be completely stationary - no matter how fast the engine revved, the treadmill would match whatever speed the car did. But we're talking about an airplane. An airplane doesn't move in the same way that ground vehicles do, obviously.

The way airplanes fly is by generating enough forward velocity to have the air under the wings lift the plane - this is explained with Bernoulli's principle. It's why the wings of an airplane look curved in cross-section. Air has to flow faster over the top of the wing to travel a longer distance in a shorter amount of time. Therefore not as much downward force is exerted when the plane reaches its takeoff speed. So how does the plane manage to move forward if its wheels are being matched?

Simple: the airplane's wheels have absolutely nothing to do with the thrust. They're there to reduce/eliminate friction. The thrust comes from the propeller, which pulls air backward and over the wings of the plane. The wheels are free-spinning - no matter what, they'll simply spin twice as fast as the airplane's speed.

It'd be like you putting on a pair of rollerblades and stepping onto a treadmill, holding onto the sidebars. The wheels spin freely, and your arms are like the plane's wings. You can easily pull yourself forward, regardless of the treadmill; it's not acting on the aspect of the system that governs motion.