ScriptNarrator:Now listen to part of a lecture in a physics class.Male ProfessorHave any of you ever wondered how, exactly, planes are able to fly, even though they’re so much heavier than air? There are actually a couple of ways we can answer that.The

Script
Narrator:

Now listen to part of a lecture in a physics class.

Male Professor

Have any of you ever wondered how, exactly, planes are able to fly, even though they’re so much heavier than air? There are actually a couple of ways we can answer that.

The first way, the uhh… easier way, I think, is based on Newton’s third law. That law says that when you PUSH something, there is push back. So, think about a wing. It’s slanted up, right? The front of the wing is higher than the back. And as the plane moves through the air, that air goes…goes under the wing. It gets pushed DOWN by the slant. And when that air is pushed down, as we said, it has to push back! It pushes up. So there’s a lot of air getting pushed down by that angle of the wing, and it’s all pushing back up, pushing the plane into the air.

The second answer has to do with something called Bernoulli’s principle, which is about how FLUIDS work. And when I say “fluids,” that includes, gases, too—not just liquids. This principle...it says that as the speed of a fluid…in this case, air...as the speed of the air DECREASES, pressure INCREASES. And also, as SPEED goes up, pressure… pressure goes down. So, in other words, the faster the air is moving, the LESS the pressure. The slower it is moving, the MORE the pressure. Get it? They’re OPPOSITE.

We won’t worry too much about how this works, but just know that a plane’s wing has a special shape. Because of that shape, air moves FASTER on the TOP of the wing than on the BOTTOM of the wing. So that means the air on TOP, where the air is moving fast, has LOW pressure… and the air on the BOTTOM of the wing, where the air is moving slowly, has HIGH pressure. The difference in pressure pushes the wing upward into the sky.