A highspeed aircraft is flying at an elevation of 8000 ft Th

A high-speed aircraft is flying at an elevation of 8.000 ft. The plane is heard 12 s after the sound was emitted. The air temperature is 20degree F. Determine the Mach number and the speed of the aircraft in mph. Gas constant R = 1716 (ft-lbf)/(slug-degreeR).

Speed of sound c = [k R T]^1/2= [ 1.4 (1716 ft lb/slug ^oR) ((20 ^oF) + (460 ^oR)) ]^1/2 = 1073.84 ft/s

Speed of aircraft = 8000/12 = 666.67 ft/s