Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
Mach Five Mach Five The is the racing car Speed Racer (Go Mifune in the Japanese version) drives in the anime series of the same name (known as ""Mach Go! Go! Go!"" in Japan). The car was designed, built, and created by "Pops Racer" (Daisuke Mifune), Speed Racer's father. It features a set of special devices which Speed Racer uses throughout the series. In the original 1967 series, the Mach Five is a white racing car with an "M" written on its hood (which does not stand for "Mach 5", but instead stands for "Mifune", both Go's last name, and the name