What is Air? | Pressure | Stable & Unstable | Volume | Weather Front | Layers
When your friend squeezes your arm, you feel pressure! That's because molecules collide with each other and things like your arm, the ground, or a tree. They exert a force on those surfaces.
Molecules in Earth’s atmosphere constantly bounce off each other and everything else around them. The force exerted by these air molecules is called air pressure. Molecules that are packed closely are at higher pressure than molecules that are more spread out. The molecules inside this balloon are at a higher pressure than the molecules outside the balloon.
What's a high pressure system?
What's a low pressure system?