Pressure Exerted by a Gas

When a gas is enclosed inside a container, it exerts an outward push on every wall it touches -- this is the pressure that can be measured with a simple gauge. Kinetic theory traces this pressure back to something entirely mechanical: every individual gas molecule, bouncing elastically off a wall, delivers a tiny impulse to that wall, and the sum of an enormous number of these impulses, each far too small to notice individually, adds up to the steady, continuous force measured macroscopically as pressure. The next few subsections build this idea into an exact formula, and then use that formula to re …