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Encyclopedia > Speed

Speed is the rate of motion, or equivalently the rate of change in position, many times expressed as distance d traveled per unit of time t. Speed can refer to: Look up speed in Wiktionary, the free dictionary Speed, rate of motion Speed, a 1994 United States film starring Keanu Reeves Speed, an IMAX documentary Amphetamines or methamphetamine (slang term) Speed, Victoria, a town in Victoria, Australia. ... This article or section is in need of attention from an expert on the subject. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... The former Weights and Measures office in Middlesex, England. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ...

Speed is a scalar quantity with dimensions distance/time; the equivalent vector quantity to speed is known as velocity. Speed is measured in the same physical units of measurement as velocity, but does not contain the element of direction that velocity has. Speed is thus the magnitude component of velocity. In physics, a scalar is a simple physical quantity that does not depend on direction, and therefore does not depend on the choice of a coordinate system. ... Quantity is a kind of property which exists as magnitude or multitude. ... 2-dimensional renderings (ie. ... Look up length, width, breadth in Wiktionary, the free dictionary. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... A vector going from A to B. In physics and in vector calculus, a spatial vector, or simply vector, is a concept characterized by a magnitude and a direction. ... In physics, velocity is defined as the rate of change of displacement or the rate of displacement. ... The magnitude of a mathematical object is its size: a property by which it can be larger or smaller than other objects of the same kind; in technical terms, an ordering of the class of objects to which it belongs. ...

In mathematical notation, it is simply:

$|v| = frac {d}{t}$

Objects that move horizontally as well as vertically (such as aircraft) distinguish forward speed and climbing speed. Look up aircraft in Wiktionary, the free dictionary. ... V speeds are speeds that define certain performance and limiting characteristics of an aircraft. ... V speeds are speeds that define certain performance and limiting characteristics of an aircraft. ...

## Units

Units of speed include:

Mach 1 ≈ 343 m/s ≈ 1235 km/h ≈ 768 mph (see the speed of sound for more detail)
c = 299,792,458 m/s
1 m/s = 3.6 km/h
1 mph = 1.609 km/h
1 knot = 1.852 km/h = 0.514 m/s

Vehicles often have a speedometer to measure the speed. Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ... SI derived units are part of the SI system of measurement units and are derived from the seven SI base units. ... Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). ... Miles per hour is a unit of speed, expressing the number of international miles covered per hour. ... A knot is a non SI unit of speed equal to one nautical mile per hour. ... A nautical mile or sea mile is a unit of length. ... An F/A-18 Hornet breaking the sound barrier. ... Sound is a vibration that travels through an elastic medium as a wave. ... Sound is a vibration that travels through an elastic medium as a wave. ... A line showing the speed of light on a scale model of Earth and the Moon The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic... Look up Vacuum in Wiktionary, the free dictionary. ... In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ... Sound is a vibration that travels through an elastic medium as a wave. ... Look up air in Wiktionary, the free dictionary. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Speedometer gauge on a car, showing the speed of the vehicle in miles and kilometres per hour on the outâ€“ and inside respectively. ...

## Average speed

Speed as a physical property represents primarily instantaneous speed. In real life we often use average speed (denoted $|tilde{v}|$), which is rate of total distance (or length) and time interval. For example, if you go 60 miles in 2 hours, your average speed during that time is 60/2 = 30 miles per hour, but your instantaneous speed may have varied. A physical property is any aspect of an object or substance that can be measured or perceived without changing its identity. ... Look up Rate in Wiktionary, the free dictionary. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... Look up length, width, breadth in Wiktionary, the free dictionary. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ...

In mathematical notation:

$|tilde{v}| = frac{Delta l}{Delta t}.$

Instantaneous speed defined as a function of time on interval [t0,t1] gives average speed: A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ...

$|tilde{v}| = frac{int_{t_0}^{t_1} |v|(t) , dt}{Delta t}$

while instant speed defined as a function of distance (or length) on interval [l0,l1] gives average speed:
Distance is a numerical description of how far apart objects are at any given moment in time. ... Look up length, width, breadth in Wiktionary, the free dictionary. ...

$|tilde{v}| = frac{Delta l}{int_{l_0}^{l_1} frac{1}{|v|(l)} , dl}$

It is often intuitively expected, but incorrect, that going half a distance with speed | v | a and second half with speed | v | b, produces total average speed $|tilde{v}| = frac{|v|_a + |v|_b}{2}$. The correct value is $|tilde{v}| = frac{2}{frac{1}{|v|_a} + frac{1}{|v|_b}}$
(Note that the first is a proper arithmetic mean while the second is a proper harmonic mean). In mathematics and statistics, the arithmetic mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided by the number of items in the list. ... In mathematics, the harmonic mean (formerly sometimes called the subcontrary mean) is one of several kinds of average. ...

Average speed can be derived also from speed distribution function (either in time or on distance): In mathematics, a probability density function (pdf) is a function that represents a probability distribution in terms of integrals. ...

$|v| sim D_t; Rightarrow ; |tilde{v}| = int |v| D_t(|v|) , d|v|$
$|v| sim D_l; Rightarrow ; |tilde{v}| = frac{1}{int frac{D_l(|v|)}{|v|} , d|v|}$

## Examples of different speeds

Below are some examples of different speeds (see also main article Orders of magnitude (speed)): To help compare different orders of magnitude, the following list describes various speed levels between 1. ...

• Speed of a common snail = 0.001 m/s; 0.0036 km/h; 0.0023 mph.
• A brisk walk = 1.667 m/s; 6 km/h; 3.75 mph.
• Olympic sprinters (average speed over 100 metres) = 10 m/s; 36 km/h; 22.5 mph.
• Speed limit on a French autoroute = 36.111 m/s; 130 km/h; 80 mph.
• Top cruising speed of a Boeing 747-8 = 290.947 m/s; 1047.41 km/h; 650.83 mph.
• Official air speed record = 980.278 m/s; 3,529 km/h; 2,188 mph.
• Space shuttle on re-entry = 7,777.778 m/s; 28,000 km/h; 17,500 mph.

The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... The five Olympic rings were designed in 1913, adopted in 1914 and debuted at the Games at Antwerp, 1920. ... An autoroute. ... The Boeing 747-8 is the latest variant of the Boeing 747, officially announced on November 14, 2005 as an evolutionary development of the Boeing 747-400. ... Determining the fastest aircraft in the world is difficult, because of the wide variety of designs. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ...

Look up swiftness in
Wiktionary, the free dictionary.

Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... In physics, velocity is defined as the rate of change of displacement or the rate of displacement. ... V speeds are speeds that define certain performance and limiting characteristics of an aircraft. ... To help compare different orders of magnitude, the following list describes various speed levels between 1. ... Paul Virilio (born 1932 in Paris) is a cultural theorist and urbanist. ... A projectile is any object sent through space by the application of a force. ...

## References

Results from FactBites:

 Speed - Wikipedia, the free encyclopedia (487 words) Speed (symbol: v) is the rate of motion, or equivalently the rate of change of position, expressed as distance d moved per unit of time t. Speed is a scalar quantity with dimensions distance/time; the equivalent vector quantity to speed is known as velocity. Speed is thus the magnitude component of velocity.
 Speed (film) - Wikipedia, the free encyclopedia (2065 words) Speed is a 1994 film directed by Jan de Bont, starring Keanu Reeves, Sandra Bullock (her breakout role), Jeff Daniels and Dennis Hopper. Even though she lost her license for speeding, she must, ironically, speed through the congested city to keep the bus moving. Speed was the last movie hosted by Graham Yost's father Elwy Yost on TVO's Saturday Night at the Movies.
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