Speed

Speed is the rate of motion expressed as distance moved per unit time. Speed is a scalar; the equivalent vector quantity is known as velocity.

Units of speed include:

• metre per second (symbol m.s^-1), the SI derived unit
• kilometre per hour, km.h^-1
• mile per hour
• knot (nautical miles per hour)
• Mach, where Mach 1 is the speed of sound; Mach n is n times as fast.

1 m.s^-1 = 3.6 km.h^-1

1 mph = 1.609 km.h^-1

1 knot = 1.852 km.h^-1 = 0.514 m.s^-1.

Mach 1 = ca. 1200 km.h^-1 = ca. 330 m.s^-1;

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Speed is also:

• slang for amphetamines
• an American film: see Speed (movie).