4: Pressure in gases

fluid

A substance with no fixed shape - gas/liquid

pressure

ratio of force to surface area in N/m², how it causes stress in solids

fluid pressure

When atoms/molecules in a gas or liquid collide in all directions of surface.

fluid pressure formula

force (N)/ area (m²) in N/m²

how to increase gas pressure

* squash or heat it
* same amount of gas in smaller volume means more collisions between air molecules and container walls → higher pressure

atmospheric pressure

Pressure caused by the weight of the air above a surface.

Why is atmospheric pressure bigger near the ground?

More air above you → weight of air is heavier

Why does gas have a higher density at sea level?

* Gravity pulls air molecules towards Earth
* Makes it harder for mountain climbers to breathe

Why can’t you feel atmospheric pressure?

It is cancelled out by the pressure of the gases and liquids your body is pushing out

Why do mountaineers take oxygen tanks?

* Atmospheric pressure is small →the higher you are, the less air there is above you
* Gravity pulls air molecules towards Earth