Supersonic aircrafts speed is often measured in Mach, what is that?

kkanadekkanade Forum Coordinator
Supersonic aircrafts speed is often measured in Mach, what is that? 
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  • prajputprajput Member

    Hi @kkanade  !

    The Mach number is defined as the ratio of the flow velocity (V) to the speed of sound (c):

    M = V/c

    This number defines whether a flow or vehicle is moving at subsonic (M<1), sonic (M=1), or supersonic (M>1) speed. Namely, whether is traveling slower, at the same speed, or faster than the speed of sound.

    If a vehicle travels at Mach 2 it means that is moving at twice the speed of sound.

  • kkanadekkanade Forum Coordinator

    Hi @prajput  ,

    How much is the speed of sound?

  • Hello @kkanade , allow me to answer this one,

    The speed of sound does not have a specific value but it depends on the medium. Indeed, it represents the velocity of propagation of a sound wave through a medium. Its more general expression, valid for all gases, is:

    a = sqrt[ (dp/drho)_s ]

    where s indicates an isentropic process.

    A more commonly used expression, for the speed of sound, is the one for calorically perfect gases:

    a = sqrt( gamma*R*T)

    where

    gamma is the ratio of the specific heats

    R is the specific gas constant

    T is the medium temperature

    Hope that answers your question! 😎

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