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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 fastest automobile in 2015 was the Porsche 918 Spyder, which is a hybrid vehicle that takes 2.2 seconds to accelerate from 0 to 60 mph. [2] [3] In June 2021, the Tesla Model S Plaid was measured to accelerate from 0 to 60 mph in 1.98 seconds, not including first foot of rollout. [4]
Railroads also implement their own limits and enforce speed limits. Speed restrictions are based on a number of factors including curvature, signaling, track condition, and the presence of grade crossings. Like road speed limits in the United States, speed limits for tracks and trains are measured in miles per hour (mph).
The speed at which light propagates through transparent materials, such as glass or air, is less than c; similarly, the speed of electromagnetic waves in wire cables is slower than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v ).
At 0 °C (32 °F), the speed of sound in air is about 331 m/s (1,086 ft/s; 1,192 km/h; 740 mph; 643 kn). [1] The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior.
Point system may lead to license suspension. Exceeding the speed limit by more than 15 mph (24 km/h) with a speed of greater than 55 mph (89 km/h) or travelling faster than 80 mph (129 km/h) results in a minimum 30-day license suspension. [67] Pennsylvania: $35 [68] plus court and other costs. All fines doubled in active work zones. Absolute
Speed is the magnitude of velocity (a vector), which indicates additionally the direction of motion. Speed has the dimensions of distance divided by time. 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).
Airspeed is commonly given in knots (kn). Since 2010, the International Civil Aviation Organization (ICAO) recommends using kilometers per hour (km/h) for airspeed (and meters per second for wind speed on runways), but allows using the de facto standard of knots, and has no set date on when to stop.