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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).
Angular frequency (or angular speed) is the magnitude of the vector quantity that is angular velocity. The term angular frequency vector is sometimes used as a synonym for the vector quantity angular velocity. [13] One revolution is equal to 2π radians, hence [13] [14]
The term tachyon comes from the Greek: ταχύς, tachus, meaning swift. [6]: 515 The complementary particle types are called luxons (which always move at the speed of light) and bradyons (which always move slower than light); both of these particle types are known to exist.
The scalar absolute value of velocity is called speed, being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s or m⋅s −1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector.
A speed hump (also called a road hump, or undulation, [17] and speed ramp) is a rounded traffic calming device used to reduce vehicle speed and thus sound volume on residential streets. Humps are placed across the road to slow traffic and are often installed in a series of several humps to prevent cars from speeding before and after the hump.
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Measuring the 0 to 60 mph speed of vehicles is usually done in a closed setting such as a race car track or closed lot used for professional drivers. This is done to reduce risk to the drivers, their teams, and the public. The closed course is set up for test-drives in order to reduce any variables, such as wind, weather, and traction.
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