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Abbreviations for "kilometres per hour" did not appear in the English language until the late nineteenth century. 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 ...
Special relativity. The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour).
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
A light-year, alternatively spelled light year (ly or lyr[ 3 ]), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km (Scientific notation: 9.4607304725808 × 10 12 km), which is approximately 5.88 trillion mi.
Pace [6] in minutes per kilometre or mile vs. slope angle resulting from Naismith's rule [7] for basal speeds of 5 and 4 km / h. [n 1]The original Naismith's rule from 1892 says that one should allow one hour per three miles on the map and an additional hour per 2000 feet of ascent.
Preferred walking speed. The preferred walking speed is the speed at which humans or animals choose to walk. Many people tend to walk at about 1.42 metres per second (5.1 km/h; 3.2 mph; 4.7 ft/s). [1][2][3] Individuals may find slower or faster speeds uncomfortable. Horses have also demonstrated normal, narrow distributions of preferred walking ...
The lowest official classification used in the North Indian Ocean is a depression, which has 3-minute sustained wind speeds of between 17 and 27 kn (20 and 31 mph; 31 and 50 km/h). [21] Should the depression intensify further then it will become a deep depression, which has winds between 28 and 33 kn (32 and 38 mph; 52 and 61 km/h). [ 21 ]
Speed of sound. The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.91 s or one mile in 4.69 s.