If a container has n molecules each of mass m, the pressure inside is P = \(\frac{1}{3}\frac{M}{V}C^2,\) where V is the volume of the container and c is the root mean square speed of the molecules. It is also written as
P = \(\frac{1}{3}\frac{M}{V}c^2\)
= \(\frac{1}{2}ρc^2\)