How fast is a mark?
A Mach number is a ratio of an objects speed in a given medium to the speed of sound in that medium. Mach 1 is the speed of sound, around 761 mph, or 1224.7 kilometers per hour, at sea level on a standard day. For example, Mach 5 would be 3805 mph, or 6123.5 kilometers per hour, at sea level.
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