ok let it be only pilot would know the true speed, lets become pilots u know more planes for learning more planes to crash....
ill try to find it, but u know govt or armed forces will never let enemies know about our weaknesses.....
Pl read this.
Dear dude,
speed of sound is give by equation c=Square root(k/rho) where, k=Bulk modulus and rho=Density of Fluid.
But, Density of fluid changes with respect to pressure because by ideal gas law states that p=rho*r*t
where p=pressure,rho=density,r=gas constant and t=temperature in Kelvin.
but the pressure changes with respect to altitude and is give by, p=-(rho*g*z) where p=pressure,rho=density and z=Height,g=Gravitational Acceleration;
as the altitude increases pressure decreases,decreasing the density and thus cancelling out each other and hence no effect on Ideal Gas(AIR), BUT,
as we know
c=Square root(k/rho) and k=gamma*pressure where gamma=adiabatic index and is further given by
gamma=cp/cv;
cp=specific heat at constant pressure and cv=specific heat at constant volume;
so all in all the Speed of sound depends upon cp and cv which depends on temperature. But temperature depends upon Altitude it decreases for Troposphere and stays constant after tropopause till 20km;
so from 0-11km speed of sound decreases decreasing Mach number and after 11km to 20km it remains constant;
in Aeronautics specially for airplane design we consider altitude only from 0km to 22km.
Thanks.