Metre per second
Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.
The official SI symbolic abbreviation is m·s−1, or equivalently either m/s or 
.[1] Where metres per second are several orders of magnitude too slow to be convenient, such as in astronomical measurements, velocities may be given in kilometres per second, where 1 km/s is 1000 metres per second.
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Conversions
1 m/s is equivalent to:
- = 3.6 km·h−1 (exactly)
- ≈ 3.2808 feet per second (approximately)
- ≈ 2.2369 miles per hour (approximately)
- ≈ 1.9438 knots (approximately)
1 foot per second = 0.3048 m·s−1 (exactly)
1 mile per hour = 0.44704 m·s−1 (exactly)
1 km·h-1 ≈ 0.2778 m·s−1 (approximately)
1 kilometre per second is equivalent to:
- ≈ 0.6213 miles per second (approximately)
- ≈ 2237 miles per hour (approximate)
Relation to other measures
Although m·s−1 is an SI derived unit, it could be viewed as more fundamental than the metre, since the latter is derived from the speed of light in a vacuum, which is defined as exactly 299 792 458 m·s−1 by the BIPM.[2] It follows that one metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of one second.