# Lesson 01 – All About Air

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## Vocabulary

Air is a mixture of gases that have no smell or taste, but can transmit sound.

Flight is the motion of an object in or through Earth’s atmosphere or through space.

Mass is the amount of matter in an object; the mass of an object remains the same no matter where it is.

Weight is the measure of the amount of force acting on a mass due to the pull of gravity; the same object will weigh more on Earth than it will on the Moon, due to the Moon’s lower gravity.

Pressure is the act of one force pushing against or pressing down on another force or on an object (e.g., when pressure is applied to a wet sponge, the water comes out).

Gravity is the force that attracts objects toward one another (e.g., gravity pulls objects toward the ground).

Air Pressure is the weight of the air pressing down on everything on Earth.

Aerodynamics is the study of the movement of air and other gases, and the way solid objects, such as planes, are affected as they move through it.

Air is all around you. You cannot live without air. Air makes flight possible, too. Planes and rockets, birds and bumblebees—every type of flying thing uses air.

## Some Properties of Air

Unless the air around you is heavily polluted, you cannot see, taste, or smell the air. If you think you cannot feel air, take a deep breath. You can feel air rushing into your lungs.

Air also has mass or weight. A balloon weighs more after you fill the balloon with air. You experience the pressure air exerts on every surface. Closer to the ground, more air is pushing down on top of you and Earth’s gravity pulls more. The higher up you go, the less air pressure there is. Air becomes thinner and more spread out.

When it comes to flying, pressure is probably the most important property of air. Air pushes on every surface. Try this: Hold two pieces of paper out in front of you, about 8 cm apart. Now blow between them. Did you expect the sheets to fly apart? They move closer together because the force of air on either side of the paper is unbalanced. The air moves quickly between the two papers. The moving air exerts less pressure than the air pressing on the outsides of the papers.

Aerodynamics means the motion of air and how air affects everything moving through it. People who design flying things have to know all about aerodynamics. This helps them build aircraft that fly efficiently and safely through the air.

## Now Show What You Know!

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