At witch Mach numbers it is suitable to consider that Air density ρ = constant?

Question B2 a) At a given instant of time, two pressure waves, each moving at the speed of sound, emitted by a point source moving with a constant velocity in a fluid in at rest are shown in figure QB2. Determine the Mach number involved and indicate with a sketch the instantaneous location of the point source. R=5 cm 12 cm Figure QB2 R=24 cm [8 Marks] b) The gas velocity across a normal shock wave decreases from 480 m/s to 160 m/s. If the pressure and density upstream of the shock are 62 kPa and 1.5 kg/m ³, find the pressure and density downstream of the shock and the specific heat ratio of the gas. c) An aircraft is in supersonic flight at 11 km altitude on a standard day. The true air speed of the plane is 695 m/s. Calculate the flight Mach number of the aircraft. A total head tube is attached to the plane is used to sense stagnation pressure which is converted to flight Mach number by an on-board computer. However, the computer programme has ignored the normal shock wave that…