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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.
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.
Passenger trains are limited to 59 mph (95 km/h) and freight trains to 49 mph (79 km/h) on track without block signal systems. (See dark territory.) Trains without "an automatic cab signal, automatic train stop or automatic train control system "may not exceed 79 mph (127 km/h)." The order was issued in 1947 (effective December 31, 1951) by the ...
0 to 60 mph. The time it takes a vehicle to accelerate from 0 to 60 miles per hour (97 km/h or 27 m/s), often said as just " zero to sixty " or " nought to sixty ", is a commonly used performance measure for automotive acceleration in the United States and the United Kingdom. In the rest of the world, 0 to 100 km/h (0 to 62.1 mph) is used.
Speed limit sign in the Republic of Ireland, using "km/h.". The SI representations, classified as symbols, are "km/h", "km h −1" and "km·h −1".Several other abbreviations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "kph", [3] [4] [5] "kmph" and "km/hr" [6] as English abbreviations.
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).
Beaufort scale. A ship in a force 12 (" hurricane -force") storm at sea, the highest rated on the Beaufort scale. The Beaufort scale / ˈboʊfərt / is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale.
The knot (/ nɒt /) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s). [1][2] The ISO standard symbol for the knot is kn. [3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE), while kt is also common, especially in aviation, where it is ...