Question

Which of the following is the correct relation for mach number?

(a) M=V\(\sqrt{\frac{\rho}{\gamma P}}\)

(b) V=\(\frac{a}{M}\)

(c) M=V\(\sqrt{\frac{P}{\gamma\rho}}\)

(d) M=V\(\sqrt{\frac{\gamma p}{\rho}}\)

The question was posed to me in exam.

This intriguing question comes from Measurement of Mach Number in portion Atmosphere and Air Data Measurement of Aircraft Performance

Answer 1

Correct answer is (a) M=V\(\sqrt{\frac{\rho}{\gamma P}}\)

The explanation is: M=V\(\sqrt{\frac{\rho}{\gamma P}}\) is the correct relation for mach number in terms of pressure and density. In M=V\(\sqrt{\frac{\rho}{\gamma P}}\), M=mach number, V=velocity , ρ=density, P= pressure and γ is γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume.