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The kilometre, a unit of length, first appeared in English in 1810, [9] and the compound unit of speed "kilometers per hour" was in use in the US by 1866. [10] "Kilometres per hour" did not begin to be abbreviated in print until many years later, with several different abbreviations existing near-contemporaneously.
Knots tied at a distance of 47 feet 3 inches (14.4018 m) from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass (28-second sand-glass is the currently accepted timing) to time the operation. [9] The knot count would be reported and used in the sailing master's dead reckoning and navigation.
Final report considered speed limit change induced a 3.5 km/h (2.2 mph) speed decrease and saved 349 lives during the two years which last 20 months [128] Spain (2019) Decrease speed from 100 to 90 km/h (62 to 56 mph) In Spain the year 2019 was the best year with the fewest people killed outside a built-up area.
To convert from kilometers per hour to meters per hour, multiply the figure by 1,000 (hence the prefix kilo-from the ancient Greek language word for thousand).; To convert from meters per second to meters per hour, divide the figure by 3,600 (that is 60 * 60, i.e. 60 seconds for each of the 60 minutes).
Prior to 2009, a speed limit could be defined in kilometers per hour (km/h) as well as miles per hour (mph). The 2003 version of the MUTCD stated that "speed limits shown shall be in multiples of 10 km/h or 5 mph." [118] If a speed limit sign indicated km/h, the number was circumscribed and "km/h" was written below. Prior to 2003, metric speed ...
By 0–100 km/h (62 mph) time (3.0 s or less) [ edit ] These are standing start (no rollout allowed) acceleration times measured by independent, reliable sources (thus these are not precisely comparable with the first table where even 9.5-96.6 km/h times are allowed).
Some airspeed indicators in aircraft prior to the mid-1970s indicate in miles per hour plus knots (1 knot = 1.15 mph) or kilometers per hour (1 knot = 1.85 km/h). A primary flight display with the indicated airspeed (IAS) displayed in the form of a vertical "tape" on the left.
Miles per hour (mph, m.p.h., MPH, or mi/h) is a British imperial and United States customary unit of speed expressing the number of miles travelled in one hour. It is used in the United Kingdom , the United States , and a number of smaller countries, most of which are UK or US territories, or have close historical ties with the UK or US.