Problem #$3$: Air at $122F$ and $14\mathrm{.}7$ psia flows in a rectangular duct $1ft3ft$ at a rate of $150f\frac{t^3}{s}.$ The duct is horizontal and $1000ft$ long and is made of galvanized iron. Estimate the pressure loss due to friction in this duct. Viscosity of air is $4\mathrm{.}1{10}^{-7}l{b}_f\frac{s}{f}{t}^2.$ At the end of your calculations verify whether air can be considered incompressible or not.

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