where is the root mean square speed of the molecules of the sample. The root mean square is a type of average and is found by taking the square root of the average of the squared speeds of all of the molecules:
where N is the number of molecules present. Note that the rms speed is not the same as the average speed of the molecules. However, it is usually quite close and can be considered the same.
Rearranging equation (1) and substituting from the ideal gas law gives another expression of equation (1):
