Number One: Newton’s Law of Motion
We can see another good example of this law in kites, where the forces acting on them include their own weight, the lift and drag (a force that works opposite of a moving object’s lift), and the tension in the line connecting the kite to you. When all of these forces balance out, the kite flies at a stable altitude, or height in the air. If the wind outside picks up, the kite’s altitude will increase (if you let out a bit more of its controlling line), causing the lift and drag forces to increase as well. When this happens, the forces are no longer balanced and there is a net - or total - vertical force applied on the kite, and in return, it moves vertically instead of staying in one place. If we take out the tension force of the line, we can apply this concept to an airplane!
Number Two: Bernoulli’s Principle
Another theory of interest involves motion in a fluid. David Bernoulli (1700-1782) discovered that as the velocity in a fluid increases, its pressure decreases in return. His principle applies to any fluid, and since air is a fluid, this applies to air as well. This means that airplanes can fly because the pressure above its wing is less than the pressure below its wing.
In that example, we see that there are two types of pressure: static pressure and total (or ram) pressure. When applied to a flying airplane, the static pressure would be what we’d have when the plane is flying with the wind, instead of against it. Air presses against the plane equally in all directions, with this pressure decreasing as the plane’s speed increases - which is defined as the Bernoulli principle!
Number Three: The Coanda Effect
Try it Out!
To demonstrate the Bernoulli principle, this simple experiment requires only two pieces of paper! Hold one piece of paper horizontally in each hand, close to your face. Now blow between them and you’ll see that the pieces of paper will get closer to each other, instead of farther away.
Make your own paper airplane! In the file attached to this post, we’ve created a document to help you fold your paper plane. Print it out and follow the instructions in the video to create your own paper airplane. The first step is to fold the paper in half, lengthwise along dotted line number 1. Then fold the edges of the paper down to where it’s folded in half, starting with dotted line number two, on both sides. Do the same for line number 3 and number 4. Keep the flaps on the outside so that the paper can catch some air!
“Paper Plane Vector Illustration”. Released into the public domain. Uploaded on 4/1/2017 from publicdomainvectors.org.
Kratochvil, Petr. “Flying Plane”. Released into the public domain. Uploaded on 4/2/2017 from publicdomainpictures.net
Siedlecki, Piotr. “Razorback Plane”. Released into the public domain. Uploaded on 4/1/2017 from publicdomainpictures.net