Kilometres per hour facts for kids

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Kilometres per hour
Metric speedometer from a 1992 Euro-spec Passat B3
A car speedometer that indicates measured speed in kilometres per hour
Standard: derived
Quantity: speed
Symbol: km/h
Expressed in: 1 km/h =
mph 0.621371
m/s 0.277778
knot 0.539957
ft/s 0.911344

The kilometre per hour (American English: kilometer per hour) is a unit of speed, expressing the number of kilometres travelled in one hour.

Internationally, km/h is the most commonly used unit of speed on traffic signs and speedometers.

History

Speedometer-in-driving-car
Speedometer in a driving car showing a reading of 45km/h

Although the metre was formally defined in 1799, the term "kilometres per hour" did not come into immediate use. The Dutch on the other hand adopted the kilometre in 1817 but gave it the local name of the mijl.

Several representations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "km/h", "kmph" and "km/hr" as English abbreviations. Abbreviations for "kilometres per hour" did not appear in the English language until the late nineteenth century. In Australian unofficial usage, km/h is sometimes pronounced and written as klicks or clicks.

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Kilometres per hour Facts for Kids. Homework Help - Kiddle Encyclopedia.