Convert Speed

Dimension LT-1
Common Symbol(s) V
SI Unit(s) m·s-1
Imperial/US Unit(s) mph
Other Unit(s) knot
Unit conversions
1 m·s-1 in ... ... is equal to ...
Metric unit(s) 3.6 km·h-1
Imperial/US unit(s) 2.237 mph
Nautical unit(s) 1.944 knot

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Metric Conversion
Kilometre per second [km/s]
Metre per second [m/s]
Kilometre per hour [km/h]
Millimetre per second [mm/s]
Micrometre per second [µm/s]
Imperial/US Conversion
Mile per second
Mile per hour [mph]
Foot per second [ft/s]
Nautical Conversion
Other Conversion
Speed of light [c]
Speed of sound
Human walk
Common snail

In everyday use and in kinematics, the speed of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.

Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second, but the most common unit of speed in everyday usage is the kilometre per hour or, in the US and the UK, miles per hour. For air and marine travel the knot is commonly used.

The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.

This article uses material from the Wikipedia article "Speed", which is released under the Creative Commons Attribution-Share-Alike License 3.0.