Instruct: Given a question, retrieve passages that answer the question.
Query: What is the difference between speed and velocity?
Relativistic speed refers to speed at which relativistic effects become significant to the desired accuracy of measurement of the phenomenon being observed. Relativistic effects are those discrepancies between values calculated by models considering and not considering relativity. Related words are velocity, rapidity, and celerity which is proper velocity. Speed is a scalar, being the magnitude of the velocity vector which in relativity is the four-velocity and in three-dimension Euclidean space a three-velocity. Speed is empirically measured as average speed, although current devices in common use can estimate speed over very small intervals and closely approximate instantaneous speed. Non-relativistic discrepancies include cosine error which occurs in speed detection devices when only one scalar component of the three-velocity is measured and the Doppler effect which may affect observations of wavelength and frequency.Relativistic effects are highly non-linear and for everyday purposes are insignificant because the Newtonian model closely approximates the relativity model. In special relativity the Lorentz factor is a measure of time dilation, length contraction and relativistic mass increase of a moving object.
While comparing between various classes of animals, a different unit is used, body length per second for organisms. The fastest organism on earth, relative to body length, is the South Californian mite "Paratarsotomus macropalpis", which has a speed of 322 body lengths per second. The equivalent speed for a human running as fast as this mite would be . This is far in excess of the previous record holder, the Australian tiger beetle, "Cicindela eburneola", the fastest insect in the world relative to body size, which has been recorded at or 171 body lengths per second. The cheetah, the fastest land mammal, scores at only 16 body lengths per second while Anna's hummingbird has the highest known length-specific velocity attained by any vertebrate
When accelerating or braking a vehicle equipped with tires, the observed angular velocity of the tire does not match the expected velocity for pure rolling motion, which means there appears to be apparent sliding between outer surface of the rim and the road in addition to rolling due to deformation of the part of tire above the area in contact with the road. When driving on dry pavement the fraction of slip that is caused by actual sliding taking place between road and tire contact patch is negligible in magnitude and thus does not in practice make slip ratio dependent on speed. It is only relevant in soft or slippery surfaces, like snow, mud, ice, etc and results constant speed difference in same road and load conditions independently of speed, and thus fraction of slip ratio due to that cause is inversely related to speed of the vehicle. The difference between theoretically calculated forward speed based on angular speed of the rim and rolling radius, and actual speed of the vehicle, expressed as a percentage of the latter, is called ‘slip ratio’. This slippage is caused by the forces at the contact patch of the tire, not the opposite way, and is thus of fundamental importance to determine the accelerations a vehicle can produce.
The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if proper distance and cosmological time are used to calculate the speeds of these galaxies. However, in general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any simple relation to velocity calculated locally. (See comoving distance for a discussion of different notions of 'velocity' in cosmology.) Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the "expansion of space" between galaxies. This expansion rate is thought to have been at its peak during the inflationary epoch thought to have occurred in a tiny fraction of the second after the Big Bang (models suggest the period would have been from around 10 seconds after the Big Bang to around 10 seconds), when the universe may have rapidly expanded by a factor of around 10 to 10.
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The Sun 1,447,959 -7%
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Depending on the rifle, bullets typically travel between 800 and 1000 m/s (2600 and 3400 feet per second) at the moment they leave the rifle's barrel. The bullet slows down considerably due to friction with the air over a distance. The distance a bullet will travel is determined by its shape, weight, launch velocity and launch angle as with any projectile, the study of which is referred to as external ballistics.
Ray is a one side infinite geodesic which is minimizing on each interval
It is the fastest land animal. Cheetahs can reach speeds of in short bursts, but the top end speed of the cheetah is disputed by more recent measurements. The average speed of a cheetah while hunting is about .
Open-wheeled racing is among the fastest in the world. Formula 1 cars can reach speeds in excess of . At Autodromo Nazionale Monza, Antônio Pizzonia of BMW Williams F1 team recorded a top speed of in the 2004 Italian Grand Prix. Since the end of the V10 era in 2006 speeds like this have not been reached, with contemporary machinery reaching around . It is difficult to give precise figures for the absolute top speeds of Formula 1 cars, as the cars do not have speedometers as such and the data are not generally released by teams. The 'speed traps' on fast circuits such as Monza give a good indication, but are not necessarily located at the point on the track where the car is travelling at its fastest. BAR Honda team recorded an average top speed of in 2006 at Bonneville Salt Flats with unofficial top speed reaching using modified BAR 007 Formula 1 car. Speeds on ovals can range in constant excess of , and at Indianapolis in excess of . Some sources claim that in 1996, Paul Tracy recorded a trap speed of at Michigan International Speedway. In 2000, Gil de Ferran set the one-lap qualifying record of at California Speedway. Even on tight non-oval street circuits such as the Grand Prix of Toronto, open-wheel Indy Cars attain speeds of .
Sir Isaac Newton described the motion of all objects using the concepts of inertia and force, and in doing so he found they obey certain conservation laws. In 1687, Newton published his thesis "Philosophiæ Naturalis Principia Mathematica". In this work Newton set out three laws of motion that to this day are the way forces are described in physics.
Averroes was another important philosopher, and while he was born shortly before Avempace's death, Averroes later in life would be in opposition to Avempace's theories the majority of the time. Avempace starts with a good kinematic definition of motion and construes it as a force. According to Avempace regarding freely falling objects, what is moved the a heavy body falls, is the heavy body and what moves it downward is its 'gravity' or its 'form' or 'nature'.
In 1913, Georges Sagnac showed that if a beam of light is split and sent in two opposite directions around a closed path on a revolving platform with mirrors on its perimeter, and then the beams are recombined, they will exhibit interference effects. From this result Sagnac concluded that light propagates at a speed independent of the speed of the source. The motion of the earth through space had no apparent effect on the speed of the light beam, no matter how the platform was turned. The effect had been observed earlier (by Harress in 1911), but Sagnac was the first to correctly identify the cause.
In modern scientific usage, weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a "force" that results from the action of gravity on matter: it measures how strongly the force of gravity pulls on that matter. However, in most practical everyday situations the word "weight" is used when, strictly, "mass" is meant. For example, most people would say that an object "weighs one kilogram", even though the kilogram is a unit of mass.
In everyday usage, mass and "weight" are often used interchangeably. For instance, a person's weight may be stated as 75 kg. In a constant gravitational field, the weight of an object is proportional to its mass, and it is unproblematic to use the same unit for both concepts. But because of slight differences in the strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets. Conceptually, "mass" (measured in kilograms) refers to an intrinsic property of an object, whereas "weight" (measured in newtons) measures an object's resistance to deviating from its natural course of free fall, which can be influenced by the nearby gravitational field. No matter how strong the gravitational field, objects in free fall are weightless, though they still have mass.
In a medium, light usually does not propagate at a speed equal to "c"; further, different types of light wave will travel at different speeds. The speed at which the individual crests and troughs of a plane wave (a wave filling the whole space, with only one frequency) propagate is called the phase velocity "v". An actual physical signal with a finite extent (a pulse of light) travels at a different speed. The largest part of the pulse travels at the group velocity "v", and its earliest part travels at the front velocity "v".
The phase velocity is important in determining how a light wave travels through a material or from one material to another. It is often represented in terms of a "refractive index". The refractive index of a material is defined as the ratio of "c" to the phase velocity "v" in the material: larger indices of refraction indicate lower speeds. The refractive index of a material may depend on the light's frequency, intensity, polarization, or direction of propagation; in many cases, though, it can be treated as a material-dependent constant. The refractive index of air is approximately 1.0003. Denser media, such as water, glass, and diamond, have refractive indexes of around 1.3, 1.5 and 2.4, respectively, for visible light. In exotic materials like Bose–Einstein condensates near absolute zero, the effective speed of light may be only a few metres per second. However, this represents absorption and re-radiation delay between atoms, as do all slower-than-"c" speeds in material substances. As an extreme example of light "slowing" in matter, two independent teams of physicists claimed to bring light to a "complete standstill" by passing it through a Bose–Einstein condensate of the element rubidium, one team at Harvard University and the Rowland Institute for Science in Cambridge, Mass., and the other at the Harvard–Smithsonian Center for Astrophysics, also in Cambridge. However, the popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrarily later time, as stimulated by a second laser pulse. During the time it had "stopped," it had ceased to be light. This type of behaviour is generally microscopically true of all transparent media which "slow" the speed of light.
In physics, special relativity (SR, also known as the special theory of relativity or STR) is the generally accepted and experimentally well-confirmed physical theory regarding the relationship between space and time. In Albert Einstein's original pedagogical treatment, it is based on two postulates:It was originally proposed by Albert Einstein in a paper published 26 September 1905 titled "On the Electrodynamics of Moving Bodies". The inconsistency of Newtonian mechanics with Maxwell's equations of electromagnetism and the lack of experimental confirmation for a hypothesized luminiferous aether led to the development of special relativity, which corrects mechanics to handle situations involving motions at a significant fraction of the speed of light (known as ""). As of today, special relativity is the most accurate model of motion at any speed when gravitational effects are negligible. Even so, the Newtonian mechanics model is still useful as an approximation at small velocities relative to the speed of light, due to its simplicity and high accuracy within its scope.
The precise strength of Earth's gravity varies depending on location. The nominal "average" value at Earth's surface, known as is, by definition, 9.80665 m/s. This quantity is denoted variously as , (though this sometimes means the normal equatorial value on Earth, 9.78033 m/s), , gee, or simply (which is also used for the variable local value).
The mite has been recorded at a speed of 322 body lengths per second (). This is far in excess of the previous record holder, the Australian tiger beetle "Cicindela eburneola", the fastest insect in the world relative to body size, which has been recorded at or 171 body lengths per second. The cheetah, the fastest land animal, which has been clocked at a peak of , scores at only 16 body lengths per second.
Air superiority depended on having the fastest, most maneuverable fighters, in sufficient quantity, based on well-supplied airfields, within range. The RAF demonstrated the importance of speed and maneuverability in the Battle of Britain (1940), when its fast Spitfire and Hawker Hurricane fighters easily riddled the clumsy Stukas as they were pulling out of dives. The race to build the fastest fighter became one of the central themes of World War II.
"Cutting speed" (also called "surface speed" or simply "speed") is the speed difference (relative velocity) between the cutting tool and the surface of the workpiece it is operating on. It is expressed in units of distance along the workpiece surface per unit of time, typically surface feet per minute (sfm) or meters per minute (m/min). "Feed rate" (also often styled as a solid compound, "feedrate", or called simply "feed") is the relative velocity at which the cutter is advanced along the workpiece; its vector is perpendicular to the vector of cutting speed. Feed rate units depend on the motion of the tool and workpiece; when the workpiece rotates ("e.g.", in turning and boring), the units are almost always distance per spindle revolution (inches per revolution [in/rev or ipr] or millimeters per revolution [mm/rev]). When the workpiece does not rotate ("e.g.", in milling), the units are typically distance per time (inches per minute [in/min or ipm] or millimeters per minute [mm/min]), although distance per revolution or per cutter tooth are also sometimes used.
Explanations based on increased flow speed and Bernoulli's principle first try to establish that there is higher flow speed over the upper surface, but they fail to explain correctly what causes the flow to speed up:Bernoulli-only explanations imply that a speed difference arises from causes other than a pressure difference, and that the speed difference then leads to a pressure difference by Bernoulli’s principle. This implied one-way causation is a misconception. The real cause-and-effect relationship between pressure and velocity is reciprocal. Finally, Bernoulli-only explanations don't explain how the pressure differences in the vertical direction are sustained. That is, they leave out the downward-turning part of the interaction.
The big difference can be noticed when we consider movement around a circle. When something moves in a circular path (at a constant speed, see above) and returns to its starting point, its average velocity is zero but its average speed is found by dividing the circumference of the circle by the time taken to move around the circle. This is because the average velocity is calculated by only considering the displacement between the starting and the end points while the average speed considers only the total distance traveled.
For a given gravitational potential energy at a given position, the escape velocity is the minimum speed an object without propulsion needs to be able to "escape" from the gravity (i.e. so that gravity will never manage to pull it back). Escape velocity is actually a speed (not a velocity) because it does not specify a direction: no matter what the direction of travel is, the object can escape the gravitational field (provided its path does not intersect the planet).