Flight  Unit Resource Material  

Here's how it works. We live at the bottom of an ocean -- an ocean of air. This air presses on everything, and we call that AIR PRESSURE. Bernoulli discovered that air doesn't press as hard when it's moving. The faster it moves, the less it presses.

Air Flow
  As airplanes fly, air is pushed above and below their wings. The air passing over the wing reaches the back of the wing at the same time as the air passing under the wing. The air moving over the wing - which has further to travel around the curved surface - has to go faster than the air moving underneath.
Bernoulli Lift is the force that pushes an object up, against the natural force of gravity. Lift helps a plane to overcome gravity, climb into the air and stay there during flight.

The first person to figure this out was a Swiss mathematician named Daniel Bernoulli (pronounced burr-NOO-lee) in the 18th Century. Old Bernoulli was pretty smart, as you'll see!

          Can you guess which one will go higher?         A: Curved wings                        B: Flat wings

The wings with the curved surface on the top and the flat bottom have the shape that actually creates lift.
Plane with curved wings

Air that moves slowly (the air going under the wing) creates MORE pressure than air that moves quickly (the air going over the wing). That means the air pressure pushing up on the bottom of the wing is greater than the air pressure pushing down on the top of the wing. Air Flow and Pressure
When there is more air pressure pushing up on the wing, it creates, you guessed it, LIFT. And the plane naturally lifts into the air. Plane lifting
Harold demonstrating technique Pick up a regular sheet of writing paper. Cut it the long way into a strip about two inches wide. Hold one end just under your lips - like in the drawing - and blow across the top of the paper. 

If you're doing it right, the paper will lift - just like Harold's. That's because the faster air blowing across the top of the paper creates less pressure pushing down than the still air pushing up from underneath the paper.

The result: the paper lifts and we can see that Mr. Bernoulli was a really smart fellow!

The explanation you have just learned for why lift works is called Bernoulli's Principle. Here's another way you can prove Bernoulli's Principle:

1. Get a Frisbee and a piece of wood approximately the same size.

2. Throw the Frisbee and the piece of wood. Which item demonstrates more lift? Why?

3. Can you think of a shape that would have even more lift than the Frisbee?