Mean (or) Average Speed (v-bar)

Definition. The mean (or average) speed, $\bar v$, is simply the arithmetic average of the individual speeds of all $N$ molecules in the gas: if the speeds are $v_1,v_2,v_3,\dots,v_N$, then $\bar v=(v_1+v_2+\cdots+v_N)/N$. Deriving this average from the Maxwell speed distribution (Section 9.2.8) gives the closed-form expressions

Here $M$ is the molar mass and $m$ is the mass of a single molecule. …