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SI, and hence the use of "km/h" (or "km h −1 " or "km·h −1 ") has now been adopted around the world in many areas related to health and safety [36] and in metrology [37] in addition to the SI unit metres per second ("m/s", "m s −1 " or "m·s −1 "). SI is also the preferred system of measure in academia and in education.
The record is 44.72 km/h (27.78 mph), measured between meter 60 and meter 80 of the 100 meters sprint at the 2009 World Championships in Athletics by speed. [4] [5] (Bolt's average speed over the course of this race was 37.578 km/h or 23.35 mph.) [6] Compared to quadrupedal animals, humans are exceptionally capable of endurance, but incapable of great speed. [7]
m/s ≡ 1 m/s = 1 m/s mile per hour: mph ≡ 1 mi/h = 0.447 04 m/s: mile per minute: mpm ≡ 1 mi/min = 26.8224 m/s: mile per second: mps ≡ 1 mi/s = 1 609.344 m/s: speed of light in vacuum: c: ≡ 299 792 458 m/s = 299 792 458 m/s: speed of sound in air: s: 1225 to 1062 km/h (761–660 mph or 661–574 kn) [note 1] ≈ 340 to 295 m/s: Note
1 m/s is equivalent to: = 3.6 km/h (exactly) [3] ≈ 3.2808 feet per second (approximately) [4] ≈ 2.2369 miles per hour (approximately) [5] ≈ 1.9438 knots (approximately) [6] 1 foot per second = 0.3048 m/s (exactly) [7] 1 mile per hour = 0.447 04 m/s (exactly) [8] 1 km/h = 0.2 7 m/s (exactly) [9]
To help compare different orders of magnitude, the following list describes various speed levels between approximately 2.2 × 10 −18 m/s and 3.0 × 10 8 m/s (the speed of light). Values in bold are exact.
< 1 km/h 0–0.2 m/s: 0 ft 0 m Sea like a mirror Smoke rises vertically 1 Light air 1–3 knots 1–3 mph 1–5 km/h 0.3–1.5 m/s 0–1 ft 0–0.3 m Ripples with appearance of scales are formed, without foam crests Direction shown by smoke drift but not by wind vanes 2 Light breeze 4–6 knots 4–7 mph 6–11 km/h 1.6–3.3 m/s 1–2 ft
The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). [1] It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). [2]
A series of Locomotive Acts (in 1861, 1865 and 1878) created the first numeric speed limits for mechanically propelled vehicles in the UK; the 1861 Act introduced a UK speed limit of 10 mph (16 km/h) on open roads in town, which was reduced to 2 mph (3 km/h) in towns and 4 mph (6 km/h) in rural areas by the 1865 "Red Flag Act". [16]