Speed

:For alternate uses, see special education or speed (disambiguation).

Related Topics:
Special education - Speed (disambiguation)

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Speed (symbol: v) is the rate of motion, or equivalently the rate of change of position, expressed as distance d moved per unit of time t.

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Speed is a scalar quantity with dimensions distance/time; the equivalent vector quantity to speed is known as velocity. Speed is measured in the same physical units of measurement as velocity, but does not contain the element of direction that velocity has. Speed is thus the magnitude component of velocity.

Related Topics:
Scalar - Distance - Time - Vector - Velocity - Direction

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Units of speed include:

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• metres per second, (symbol m/s), the SI derived unit
• kilometres per hour, (symbol km/h)
• miles per hour, (symbol mph)
• knots (nautical miles per hour, symbol kt)
• Mach, where Mach 1 is the speed of sound; Mach n is n times as fast.

::Mach 1 = ~343 m/s = ~1235 km/h = ~768 mi/h (see the speed of sound for more detail)

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• speed of light in vacuum (symbol c) is one of the natural units

::c = 299,792,458 m/s

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::1 m/s = 3.6 km/h

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::1 mph = 1.609 km/h

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::1 knot = 1.852 km/h = 0.514 m/s

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Vehicles often have a speedometer to measure the speed.

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The rate of change of speed with respect to time is termed acceleration.

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Speed: Average speed ►