What is air pressure?
Air is all around us, and even though it is very light, it pushes on everything. This push of air is called air pressure. Air pushes in every direction, up, down and sideways.
Key idea
Air pressure is the push of air on the surfaces of objects around us.
Seeing air pressure at work
When you drink through a straw, you suck out some air. The air pressure outside then pushes the drink up the straw into your mouth. When you blow up a balloon, the air inside pushes out and makes the balloon bigger and firm.
- A straw uses air pressure to lift a drink
- Air pressure makes a balloon firm
- Air pressure helps a rubber sucker stick
Example
A rubber sucker sticks to a smooth wall because air pressure outside pushes it firmly against the wall.
Strong and weak air pressure
A fully pumped ball is hard because the air pressure inside is high. A soft, flat ball has low air pressure inside. Pumping in more air raises the pressure, and letting air out lowers it. This is why we pump air into bicycle tyres to make them firm enough to ride on.