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Mach line[′mäk ‚līn]
A line representing a Mach wave.
A theoretical line representing the backsweep of a cone-shaped shock wave made by an assumed infinitesimally small particle moving at the same speed and along the same flight path as that of an actual body or particle. This line, as represented on any plane bisecting the shock-wave cone, forms an angle with the flight path usually somewhat more acute than the angle formed by the shock wave of the actual body. A very weak shock forms an angle approximating the angle of the mach line. See Mach cone and Mach wave.