# Mach number: Quiz

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More interesting facts on Mach number

Question 1: This is somewhat reminiscent of the early modern ocean sounding unit "mark" (a synonym for ________), which was also unit-first, and may have influenced the use of the term Mach.
Dutch languagePolish languageFathomGerman language

Question 2: Because the Mach number is often viewed as a ________ rather than a unit of measure, with Mach, the number comes after the unit; the second Mach number is "Mach 2" instead of "2 Mach" (or Machs).
Reynolds numberDimensionless quantityFluid dynamicsKeulegan–Carpenter number

Question 3: Assuming air to be an ________, the formula to compute Mach number in a subsonic compressible flow is derived from Bernoulli's equation for M<1:[3]
Maxwell–Boltzmann statisticsStatistical mechanicsIdeal gasTemperature

Question 4: The Mach number is named after Czech/Austrian physicist and philosopher ________.
Ernst MachPhysicsLudwig BoltzmannAlbert Einstein

Question 5: the sound barrier) a large pressure difference is created just in front of the ________.

Question 6: As the Mach number increases, so does the strength of the ________ and the Mach cone becomes increasingly narrow.
SunShock waveExplosive materialMoving shock

Question 7: It is this shock wave that causes the ________ heard as a fast moving aircraft travels overhead.
Supersonic transportLightningSonic boomSupersonic

Question 8: As it is defined as a ratio of two speeds, it is a ________.
Fluid dynamicsKeulegan–Carpenter numberReynolds numberDimensionless quantity

Question 9: The ________ in vacuum corresponds to a Mach number of approximately 880,000 (relative to air at sea level).
SunSpeed of lightOpticsPhoton

Question 10: Such nozzles are called ________ and in extreme cases they are able to reach incredible, hypersonic speeds (Mach 13 at sea level).
Rocket engineChoked flowDe Laval nozzleRocket engine nozzle