Vocabulary

air pressure: The force exerted by air on an area. Units: metric is newtons per square meter; English is pounds per square inch.

Bernoulli's principle: A natural physical law that pressure exerted by a fluid decreases as the rate of flow increases.

fluid: Any substance in which the molecules can move around freely. A fluid is any gas or liquid, such as air and water.

force: A push or pull on an object.

lift: The force resulting from the difference in air pressure above and below the wings that causes aircraft to move upwards.

What is air

Air is a collection of molecules—very small particles that we cannot see—that cover the surface of the Earth. Air is comprised of 78% nitrogen, 21% oxygen, and the remaining 1% is mostly argon and carbon dioxide.

Blow onto your hand. What is happening?

Why doesn't air around the planet escape to space?

Gravity pulls on air just like it pulls on a person and all objects. The weight of air is called air pressure and it pushes on us all the time. The existence of air pressure is what enables airplanes to fly.

Icarus

Leonardo da Vinci

Daniel Bernoulli

discovered that water and air move faster over curved surfaces than they do over flat ones. He also discovered that as the air or water moved faster, the pressure exerted by the fluid decreased. This critical discovery, known as Bernoulli's principle, paved the way for modern airplanes.

Orville and Wilbur Wright

What Is Air Pressure?

Our atmosphere could be described as a sea of air that is about 80 kilometers thick surrounding the planet. All of that air piled on top of us is pulled down by gravity (see Figure 1). In fact, the air pushes against us in all directions. This is air pressure. Refer to the Air Pressure activity to have students learn more about the concept