Expression for Pressure due to an ideal Gas #8211; On the basic of assumption of kinetic theory of gases, we can do mathematical calculation to find expression for pressure exerted by a gas. We find that [ pV = 1/3 m/N (v¯<sup>2</sub>) = 1/3 mN v<sup>2</sup><sub>rms</sub> ] Root mean square speed, v<sub>rms</sub> = √v¯<sup>2</sup>