An airplane flies at an elevation of 20,000 ft, where the atmospheric pressure is 45 kPa and the temperature is -24°C. A pitot-static tube mounted on the plane in the free-stream gives a differential manometer reading equivalent to 8.5 inches of H2O. Estimate the speed of the plane, assuming incompressible flow. Assume air to be an ideal gas with particular gas constant 287 J/kg K.
(Hint: Differential manometer reading gives you the difference of height between the two columns of the U-tube. This can be used to find out the pressure difference of the two tubes). Density of water = 997 kg/m3.