How do airplanes stay in the air?
A lot of people wonder why aeroplanes can stay in the air, and it has to do with Bernoulli. Bernoulli's principle is partially responsible for keeping aeroplanes in the sky. Bernoulli said, where there's moving air, there's low pressure. This little toy might be able to explain that. This is a little helicopter toy, and it is powered by a balloon. When I blow the balloon up, I have air pressure in there, and when I attach it here and I let some of the air out, you'll hear a noise. Now, not only noise is coming out of there, but some of the air is going through each of these blades, out this way, causing the helicopter to spin. As it spins through the air like that, the wind that's going across these wings, like an aeroplane wing, has to go over the top of the wing faster than the bottom. So, if we have moving air going across the top of the wing, and moving air is low pressure, what do we have on the bottom of the wing? We then have high pressure, and that's what gives it lift. So, let's just try this. Lift off! Bernoulli's principle did it again! It's good to know that planes stay up in the air. They do come down, too, because they have to land. All an aeroplane does when it lands is it loses speed. Air doesn't go across the wing as fast and it loses its lift and it starts to come down, and it's coming down because of gravity. Now gravity's a force between a very, very large object such as the planet earth and anything that's near it, and it will draw it to it. We can kind of demonstrate this with a helicopter. A helicopter will go up, thanks to Bernoulli's principle, and gravity might bring it down. It did! Gravity brought it back down! How cool!
