Physics for Aviation
What is the approximate speed of sound at 59 degrees F, and what does an aircraft's Mach number express?
Answer
About 761 miles per hour; Mach number is the ratio of the speed of the aircraft to the speed of sound
In a uniform medium under given physical conditions, sound travels at approximately 761 miles per hour at 59 degrees F, the standard sea-level temperature. Mach number is the ratio of the speed of an aircraft to the speed of sound, named in honor of the Austrian scientist Ernst Mach.
Source: FAA-H-8083-30B, Ch. 5 p. 5-31 — 'Speed of Sound'
Not the answer
- About 340 miles per hour; Mach number is the ratio of the speed of the aircraft to the speed of sound
- About 761 miles per hour; Mach number is the aircraft's true airspeed in hundreds of knots
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