# What is air pressure? - R

What is Air Pressure?

What is Pressure?

To define Air Pressure, first we need to talk about Gases. Unlike Liquids (no definite shape, but definite volume) and Solids (definite shape and volume), Gases have no definite shape or volume. But, Gases can change shape and volume. If a gas was to be put into a jar, the Gas would take up the shape of the jar. If a gas was to be put into a bigger jar, it would have more volume then the other.
Speaking of volume, do you know what that is? Well, unlike liquids and solids, gases have more space between their particles. The space that these particles occupy would be defined as volume. So basically, volume is the amount of space that any object takes up, not just gas.

 Figure 1, Gas Pressure Diagram Credit To: Madi P.
Gas also has pressure. Pressure is the amount of force exerted on a given area or surface. To create pressure, Gas particles collide against inside walls. See Figure 1. Oh, and don’t forget! Oxygen, or air, is a major gas.

So the Definition of Air Pressure Is: The motion of air particles colliding with inside walls to create pressure.

What is Air Pressure?

Air Pressure is a force, a push or pull. The forces of all the individual particles of air add together to make up the pressure of the air. There’s more than one metric ton of air pushing down on us. Why don’t we get crushed? Because of something called Balanced Pressure. Balanced Pressure is when the amount of air pressure around you is canceled out by the amount of air in your body.
Also, the more air particles there are in a certain space, the more pressure. This is because there are even more air particles colliding and bouncing off inside walls. See Figure 1.

Air Pressure and Weather

Because of Air Pressure, we have different kinds of weather. For example, cold fronts, hot fronts, and stationary fronts. Sometimes, Air Pressure can result in natural disasters.
Air Pressure is also needed to predict weather. By the show of the weight of air and air pressure above a given area or changes in pressure to predict approaching storms, from summer thunderstorms to hurricanes.

You Can Feel It

 Figure 2, Snoopy and Altitude , Credit : Bing Images

You can’t physically see air pressure, but you can sure feel it. Ever noticed when you drive up mountain, or take off in an airplane, that your ear’s pop? That’s relating to Air Pressure. When you change altitude the air pressure changes, as well. Therefore, when you change altitude, the air inside your ears is greater than the air pressure outside your body. An example of air pressure is a Hot Air Balloon.

Air Pressure is not to get confused with Water Pressure, which controls if you sink or float

Glossary

Air Pressure – the motion of air particles colliding with inside walls to create pressure.
Balanced Pressure – The amount of air pressure around an object being canceled out by the amount of air in the object.
Force – A push or pull
Metric Ton – 1000 kilograms
Pressure - Pressure is the amount of force applied on a given area or surface
Volume – The amount of space an object takes up

### Citations

Air Pressure. Prod. Cochran. Cochran, 1999. Discovery Education. Web. 13 September 2012.
Anderson, David, and Scott Eberhardt. Understanding Flight. 2 Ed. New York: McGraw-Hill, 2009. Print.
Anita Ganeri. Outdoor Science. Ed. 2. New York: Dillon Press, 1993. Print.
Kalnay, Eugenia. Atmospheric Modeling, Data Assimilation and Predictability. Cambridge, England: Cambridge University Press, 2003. Web.
McGraw-Hill, Glencoe. Behavior of Fluids. The Nature of Matter: Student Edition. Columbus Ohio, 2002. Print
"Weather." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition. Encyclopædia Britannica, Inc., 2012. Web. 25 Sept. 2012. Web.