What causes air pressure?

Answer 1

Gravity. Air molecules have mass. Mass is attracted to other mass, in this case, the center of the earth. Thus the air is being pulled downward.

All the molecules of air are like guys jumping up on a pile on top of each other. The more on top, the heavier the pile is. When you are down on the bottom of the pile (like at sea level) there is a large ocean of air above you. Lots of pressure. When you get up on a mountain, there are less molecules, less pressure. Air, like water, tends to find its own level. Deeper you go, the more pressure.

Now, in a closed system like a car tire, air pressure is caused by the movement of the air molecules. The more they move, the more the pressure. Thus, temperature and pressure are directly related. If the volume is allowed to expand, then the pressure will drop, just like when you open the doors and let people all stream out of a crowded room.

Answer 2

Air pressure is the amount of air molecules in a given space. Say there is a given amount of air molecules in a soda bottle. When you crush the bottle with your hand, you are decreasing the volume inside the bottle, causing the gas molecules to go closer together and rub against each other.

Atmospheric pressure is literally caused by our atmosphere, which is locking down all gases into the air around us. There are many ways to measure atm. pressure; a common one is PSI. Average atmospheric pressure is 14.7 psi, meaning that pressing down on one square inch of land, is 14.7 pounds of air from the top of the atmosphere all the way to the ground.

Answer 3

This question could be taken two ways...in reference to the atmosphere (as in why isn't the air 'just here') and in reference to gasses in general.

Gasses exert pressure because the molecules or atoms making up the gas move. When they impact their surroundings, whether solid or liquid things or adjacent gas molecules, they exert a force and rebound.

We measure that force over an area as pressure.

Answer 4

Air actually has a small amount of weight. If you visualize how much air is above you at any given place, it's not surprising that the air pressure comes out roughly 14 lbs. per inch or 29.58 inches of Barometric pressure.