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The kilometre per hour (SI symbol: km/h; non-SI abbreviations: kph, km/hr) is a unit of speed, expressing the number of kilometres travelled in one hour. History [ edit ]
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.
1.15078 miles per hour (approximately), 20.25372 inches per second (approximately) 1.68781 feet per second (approximately). The length of the internationally agreed nautical mile is 1 852 m. The US adopted the international definition in 1954, having previously used the US nautical mile (1 853.248 m). [6]
In the United States, it is computed per 100 million miles traveled, while internationally it is computed in 100 million or 1 billion kilometers traveled. According to the Minnesota Department of Public Safety, Office of Traffic Safety Volume of traffic, or vehicle miles traveled (VMT), is a predictor of crash incidence.
For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
On non-freeway roads, speed limits are generally held at 55 mph (89 km/h) for rural four-lane roads, 55 mph (89 km/h) for rural two-lane roads, 45–55 mph (72–89 km/h) for urban four lane roads and 40–45 (sometimes, but rarely, 50 mph) mph (64–72 km/h) for urban two lane roads, 35–45 mph for roads in commercial business areas, 30−35 ...
An electronic odometer (below the speedometer) with digital display showing 91,308 miles (146,946 km) An odometer or odograph is an instrument used for measuring the distance traveled by a vehicle, such as a bicycle or car.
The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel, the knot is commonly used. The fastest possible speed at which energy or information can travel, according to special relativity, is ...