In fluid dynamics, the Mach number (M or Ma) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound. M = u c , {\displaystyle \mathrm {M} ={\frac {u}{c}},} {\displaystyle \mathrm {M} ={\frac {u}{. where: M is the local Mach number,: u is the local flow velocity with respect to the Generally, NASA defines high hypersonic as any Mach number from 10 to 25, The Gillette Mach3 is a line of razors produced by Gillette. Contents. 1 Production; 2 All Mach3 series razor blades are interchangeable. Mach3 disposable razors lack a "blade remove" button, but it is still possible to remove and change blades
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