Birds and airplanes, and even the paper airplane you built all have one thing in common that allow them to fly: their wings! But how do wings lift something up in the air so effortlessly?
To understand how, you need to understand how an airfoil works. In most airplane wings, you might notice that the top part is curved more than the bottom part. Check out this figure:
You can see that if you look at a slice of the wing. When air flows around the wing, it changes direction. Before it hits the wing, it is flowing horizontally, but once it leaves the wing it is flowing down. To get something to change direction, you need to give it a push…think about pushing your friend when you’re both on ice skates. If you push them forward, they end up pushing you backwards.
In the same way, the airplane is pushing the air down. Because of this, the air pushes the airplane up. This force is called lift and it keeps the airplane in the sky.
Another force appears from friction. This is called drag and must be overcome by the airplane’s engines. With very strong engines, airplanes can fly very fast. So far, with special engines the fastest airplane can go over 7,000 miles per hour!