 Wall-impact speed distribution

The speed distribution of atoms striking a wall is weighted by the normal component of velocity, relative to the distribution of atoms present in the bulk. For an isotropic classical monatomic gas, the impact speed density is proportional to $v^3{e}^{-m{v}^2/(2k_{B}T)}$, and the mean impact kinetic energy is $2k_{B}T$, rather than $3k_{B}T/2$.