Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
Ford Mustang Mach 1 horsepower calculations. The following year also produced the fewest Mach 1 sales of the 1971-73 generation. There are no major differences in the '71 and '72 Mustangs externally, other than the addition of a "Mustang" script on the right side of the trunk panel (excluding Mach 1). The '72 Mach 1 also saw deletion of the pop-open gas cap, which was replaced with the standard twist-on cap found on the other Mustang models that year. The 302 Windsor remained as the base Mach 1 engine, with the 2 or 4 barrel 351 Clevelands as the only options. In 1973, the