## Saturday, December 10, 2016

### Physics behind airplane wings

As I was booking plane tickets to go home for winter break, I wondered how airplanes can fly when the force of the engine only seems to push the plane forwards and not keep the plane up. As we learned in our physics class, there must be a force in a direction opposite of the force of gravity to keep the plane flying.

When I was younger, I heard that the wings of planes are shaped in a way that creates lift. This is obviously not a satisfactory explanation, so I searched online to find out more.
Per sites online and our textbook, the wings have a curved top side, which makes the air move faster over the top. The bottom side of plane wings are flat and the air travelling by has a lower speed. According to Bernoulli’s Principle, the air on top will have a lower pressure because its velocity is high, and the air on the bottom will have a greater pressure. This pressure difference is what generates lift to keep giant metal birds in the air.

However, Explainthatstuff.com claims that this explanation is not quite perfect. The article states that “as air flows over the curved upper surface, its natural inclination is to move in a straight line, but the curve of the wing pulls it around and back down. For this reason, the air is effectively stretched out into a bigger volume,” and this lowers the air pressure. The air that flows by the bottom of a wing experiences something opposite. The air molecules are squished into a smaller volume than normal, which means the pressure increases. And this “difference in air pressure between the upper and lower surfaces causes a big difference in air speed (not the other way around, as in the traditional theory of a wing”) A problem with the traditional explanation is that there is no reason that the air on top of a wing “has to travel a bigger distance in the same time.”

This explanation makes a lot of sense to me. Either way, we know that the air flowing by the top of a wing has higher speed and lower pressure. The air flowing by the bottom of a wing has lower speed and high pressure. This pressure difference generates a force that keeps airplanes in the sky.