EXAMPLE $6\mathrm{.}3.$ Air at $2\mathrm{.}7$atm gauge and $15C$ enters a horizont$$l $75-mm$ stcel pipe that is $70m$ long. The fow rate of the entering air $q$ is $0\mathrm{.}265\frac{m^3}{s}.$ Assuming isothermal flow, what is the pressure at the discharge end of the pipe?

Solution. Use Eq$.(6\mathrm{.}49).$ The quantities needed are