p s {\displaystyle p_{s}\;} = static pressure in Pascals, Is also the basic SI unit of Pressure ρ m {\displaystyle \rho _{m}\;} = molar density of the ideal gas in mol/m3 m m {\displaystyle m_{m}\;} = mass of a mole of the ideal gas in kg/mol ρ = ρ m m m {\displaystyle \rho \ =\rho _{m}m_{m}\;} = density of the ideal gas in kg/m3 R {\displaystyle R\;} = gas constant (8.3144 J/(mol·K)), T {\displaystyle T\;} = absolute temperature in kelvins (K), M {\displaystyle M\;} = Mach number (non-dimensional), γ {\displaystyle \gamma \;} = ratio of specific heats (non-dimensional) (1.4 for air at sea level conditions), u {\displaystyle u\;} = flow speed in m/s, a {\displaystyle a\;} = speed of sound in m/s