mach number

or Mach number

noun

1. a number indicating the ratio of the speed of an object to the speed of sound in the medium through which the object is moving. : M

Mach number

noun

1. often not capital the ratio of the speed of a body in a particular medium to the speed of sound in that medium. Mach number 1 corresponds to the speed of sound Often shortened toMach

Mach number

1. The ratio of the speed of a body to the speed of sound in a particular medium, usually the Earth's atmosphere. For example, an aircraft flying through air at twice the speed of sound has a Mach number of 2. The Mach number of an aircraft travelling at a given velocity depends on the altitude of the aircraft and other atmospheric conditions that affect the speed of sound near the aircraft.
2. See also subsonic

Mach number

1. The speed of an object, measured in multiples of the speed of sound. Thus, an airplane traveling at the speed of sound is said to be at Mach 1; at twice the speed of sound, it is said to be at Mach 2.

Notes

The unit is named after Ernst Mach, an Austrian physicist of the nineteenth century.

Word History and Origins

Origin of mach number¹

First recorded in 1935–40; after Ernst Mach

Word History and Origins

Origin of mach number¹

C19: named after Ernst Mach