Answer: Speed of an object relative to sound
Notes: The Mach number is a dimensionless quantity representing the ratio of the speed of an object to the speed of sound in the surrounding medium. Named after physicist Ernst Mach, it is crucial in aerodynamics. Objects traveling faster than Mach 1 are considered supersonic, while those exceeding Mach 5 are classified as hypersonic, impacting their design and performance significantly.
