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 a cold air "snorkel" and a partial Ram Air at speed. 2004 saw only minor cosmetic changes to the Mach 1. 2004 Mach 1s can be identified by bare aluminium finished valve covers, as opposed to the 2003's black finished covers. Outside, 2004 Mach 1's wear 40th anniversary tags ahead of the doors while the 2003 has the traditional Mustang Running Pony and Tri-Color bar. The lone interior change was the deletion of the overhead "cargo net" mounted on the headliner. Despite pre-production rumors, the horsepower and torque ratings were not increased in 2004. Power rating was and . With