1.
Stokes' law
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Stokes law is derived by solving the Stokes flow limit for small Reynolds numbers of the Navier–Stokes equations. In SI units, Fd is given in Newtons, η in Pa·s, r in meters, Stokes law makes the following assumptions for the behavior of a particle in a fluid, Laminar Flow Spherical particles Homogeneous material Smooth surfaces Particles do not interfere with each other. Note that for molecules Stokes law is used to define their Stokes radius, the CGS unit of kinematic viscosity was named stokes after his work. Stokes law is the basis of the viscometer, in which the fluid is stationary in a vertical glass tube. A sphere of size and density is allowed to descend through the liquid. If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube, electronic sensing can be used for opaque fluids. Knowing the terminal velocity, the size and density of the sphere, a series of steel ball bearings of different diameters are normally used in the classic experiment to improve the accuracy of the calculation. The school experiment uses glycerine or golden syrup as the fluid, several school experiments often involve varying the temperature and/or concentration of the substances used in order to demonstrate the effects this has on the viscosity. Industrial methods include many different oils, and polymer liquids such as solutions, the importance of Stokes law is illustrated by the fact that it played a critical role in the research leading to at least three Nobel Prizes. Stokes law is important for understanding the swimming of microorganisms and sperm, also, in air, the same theory can be used to explain why small water droplets can remain suspended in air until they grow to a critical size and start falling as rain. Similar use of the equation can be made in the settlement of fine particles in water or other fluids, requiring the force balance Fd = Fg and solving for the velocity V gives the terminal velocity Vs. Note that since buoyant force increases as R3 and Stokes drag increases as R, the terminal velocity increases as R2 and thus varies greatly with particle size as shown below. This velocity V is given by, V =29 μ g R2, in Stokes flow, at very low Reynolds number, the convective acceleration terms in the Navier–Stokes equations are neglected. By using some vector calculus identities, these equations can be shown to result in Laplaces equations for the pressure and each of the components of the vorticity vector, ∇2 ω =0 and ∇2 p =0. For the case of a sphere in a uniform far field flow, the z–axis is through the centre of the sphere and aligned with the mean flow direction, while r is the radius as measured perpendicular to the z–axis. The origin is at the sphere centre, because the flow is axisymmetric around the z–axis, it is independent of the azimuth φ. The azimuthal velocity component in the φ–direction is equal to zero, the volume flux, through a tube bounded by a surface of some constant value ψ, is equal to 2π ψ and is constant. The Laplace operator, applied to the vorticity ωφ, becomes in this coordinate system with axisymmetry
2.
Settling
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Settling is the process by which particulates settle to the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a manner in the direction exerted by that force. For gravity settling, this means that the particles tend to fall to the bottom of the vessel. Settling is an important operation in many applications, such as mining, wastewater treatment, biological science, space propellant reignition, for settling particles that are considered individually, i. e. dilute particle solutions, there are two main forces enacting upon any particle. The primary force is a force, such as gravity. The applied force is not affected by the particles velocity. For a particle at rest no drag force will be exhibited, as the particle increases in velocity eventually the drag force and the applied force will approximately equate, causing no further change in the particles velocity. This velocity is known as the velocity, settling velocity or fall velocity of the particle. This is readily measurable by examining the rate of fall of individual particles, the terminal velocity of the particle is affected by many parameters, i. e. anything that will alter the particles drag. Hence the terminal velocity is most notably dependent upon grain size, for dilute suspensions, Stokes law predicts the settling velocity of small spheres in fluid, either air or water. This originates due to the strength of forces at the surface of the particle providing the majority of the retarding force. Stokes law applies when the Reynolds number, Re, of the particle is less than 0.1. Experimentally Stokes law is found to hold within 1% for R e ≤0.1, within 3% for R e ≤0.5 and within 9% R e ≤1.0. With increasing Reynolds numbers, Stokes law begins to break due to the increasing importance of fluid inertia. In this region the inertia of the fluid is responsible for the majority of force transfer to the particle. This constant value implies that the efficiency of transfer of energy from the fluid to the particle is not a function of fluid velocity. As such the terminal velocity of a particle in a Newtonian regime can again be obtained by equating the drag force to the applied force, resulting in the following expression w =2.4612. In the intermediate region between Stokes drag and Newtonian drag, there exists a regime, where the analytical solution to the problem of a falling sphere becomes problematic
3.
Mechanics
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Mechanics is an area of science concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. The scientific discipline has its origins in Ancient Greece with the writings of Aristotle, during the early modern period, scientists such as Khayaam, Galileo, Kepler, and Newton, laid the foundation for what is now known as classical mechanics. It is a branch of physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. It can also be defined as a branch of science which deals with the motion of, historically, classical mechanics came first, while quantum mechanics is a comparatively recent invention. Classical mechanics originated with Isaac Newtons laws of motion in Philosophiæ Naturalis Principia Mathematica, both are commonly held to constitute the most certain knowledge that exists about physical nature. Classical mechanics has especially often been viewed as a model for other so-called exact sciences, essential in this respect is the relentless use of mathematics in theories, as well as the decisive role played by experiment in generating and testing them. Quantum mechanics is of a scope, as it encompasses classical mechanics as a sub-discipline which applies under certain restricted circumstances. According to the principle, there is no contradiction or conflict between the two subjects, each simply pertains to specific situations. The correspondence principle states that the behavior of systems described by quantum theories reproduces classical physics in the limit of quantum numbers. Quantum mechanics has superseded classical mechanics at the level and is indispensable for the explanation and prediction of processes at the molecular, atomic. However, for macroscopic processes classical mechanics is able to solve problems which are difficult in quantum mechanics and hence remains useful. Modern descriptions of such behavior begin with a definition of such quantities as displacement, time, velocity, acceleration, mass. Until about 400 years ago, however, motion was explained from a different point of view. He showed that the speed of falling objects increases steadily during the time of their fall and this acceleration is the same for heavy objects as for light ones, provided air friction is discounted. The English mathematician and physicist Isaac Newton improved this analysis by defining force and mass, for objects traveling at speeds close to the speed of light, Newton’s laws were superseded by Albert Einstein’s theory of relativity. For atomic and subatomic particles, Newton’s laws were superseded by quantum theory, for everyday phenomena, however, Newton’s three laws of motion remain the cornerstone of dynamics, which is the study of what causes motion. In analogy to the distinction between quantum and classical mechanics, Einsteins general and special theories of relativity have expanded the scope of Newton, the differences between relativistic and Newtonian mechanics become significant and even dominant as the velocity of a massive body approaches the speed of light. Relativistic corrections are also needed for quantum mechanics, although general relativity has not been integrated, the two theories remain incompatible, a hurdle which must be overcome in developing a theory of everything
4.
Flight
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Flight is the process by which an object moves, through an atmosphere or beyond it, as in the case of spaceflight. This can be achieved by generating lift, propulsive thrust, aerostatically using buoyancy. Many things fly, from natural aviators such as birds, bats and insects to human inventions such as missiles, aircraft such as airplanes, helicopters and balloons, to rockets such as spacecraft. Humans have managed to construct lighter than air vehicles that raise off the ground and fly, an aerostat is a system that remains aloft primarily through the use of buoyancy to give an aircraft the same overall density as air. Aerostats include free balloons, airships, and moored balloons, an aerostats main structural component is its envelope, a lightweight skin that encloses a volume of lifting gas to provide buoyancy, to which other components are attached. Aerostats are so named because they use aerostatic lift, a buoyant force that does not require movement through the surrounding air mass to effect a lifting force. By contrast, aerodynes primarily use aerodynamic lift, which requires the movement of at least some part of the aircraft through the surrounding air mass. Some things that fly do not generate propulsive thrust through the air, for example, some other things can exploit rising air to climb such as raptors and man-made sailplane gliders. However most other birds and all powered aircraft need a source of propulsion to climb, the only groups of living things that use powered flight are birds, insects, and bats, while many groups have evolved gliding. The extinct Pterosaurs, an order of reptiles contemporaneous with the dinosaurs, were very successful flying animals. Each of these groups wings evolved independently, bats are the only mammals capable of sustaining level flight. Flying frogs use greatly enlarged webbed feet for a similar purpose, flying snakes also use mobile ribs to flatten their body into an aerodynamic shape, with a back and forth motion much the same as they use on the ground. Flying fish can glide using enlarged wing-like fins, and have been observed soaring for hundreds of meters and it is thought that this ability was chosen by natural selection because it was an effective means of escape from underwater predators. The longest recorded flight of a fish was 45 seconds. Most birds fly, with some exceptions, the largest birds, the ostrich and the emu, are earthbound, as were the now-extinct dodos and the Phorusrhacids, which were the dominant predators of South America in the Cenozoic era. The non-flying penguins have wings adapted for use under water and use the same wing movements for swimming that most other birds use for flight, most small flightless birds are native to small islands, and lead a lifestyle where flight would offer little advantage. Among living animals that fly, the wandering albatross has the greatest wingspan, up to 3.5 meters, most species of insects can fly as adults. Insect flight makes use of either of two basic models, creating a leading edge vortex, found in most insects, and using clap and fling
5.
Projectile
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A projectile is any object thrown into space by the exertion of a force. Although any object in motion through space may be called a projectile, mathematical equations of motion are used to analyze projectile trajectory. Blowguns and pneumatic rifles use compressed gases, while most other guns and cannons utilize expanding gases liberated by sudden chemical reactions, light-gas guns use a combination of these mechanisms. Railguns utilize electromagnetic fields to provide a constant acceleration along the length of the device. Some projectiles provide propulsion during flight by means of an engine or jet engine. In military terminology, a rocket is unguided, while a missile is guided, note the two meanings of rocket, an ICBM is a guided missile with a rocket engine. An explosion, whether or not by a weapon, causes the debris to act as high velocity projectiles. An explosive weapon, or device may also be designed to produce high velocity projectiles by the break-up of its casing. Many projectiles, e. g. shells, may carry a charge or another chemical or biological substance. Aside from explosive payload, a projectile can be designed to cause damage, e. g. fire. Typical kinetic energy weapons are blunt projectiles such as rocks and round shots, pointed ones such as arrows, among projectiles that do not contain explosives are those launched from railguns, coilguns, and mass drivers, as well as kinetic energy penetrators. Other types of weapons are accelerated over time by a rocket engine. In either case, it is the energy of the projectile that destroys its target. Some kinetic weapons for targeting objects in spaceflight are anti-satellite weapons, since in order to reach an object in orbit it is necessary to attain an extremely high velocity, their released kinetic energy alone is enough to destroy their target, explosives are not necessary. For example, the energy of TNT is 4.6 MJ/kg, and this saves costly weight and there is no detonation to be precisely timed. This method, however, requires direct contact with the target, some hit-to-kill warheads are additionally equipped with an explosive directional warhead to enhance the kill probability. With regard to weapons, the Arrow missile and MIM-104 Patriot PAC-2 have explosives, while the Kinetic Energy Interceptor, Lightweight Exo-Atmospheric Projectile. A kinetic projectile can also be dropped from aircraft and this is applied by replacing the explosives of a regular bomb with a non-explosive material, for a precision hit with less collateral damage
6.
Bullet
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The word bullet is a firearm term. A bullet is a projectile expelled from the barrel of a firearm, the term is from Middle French and originated as the diminutive of the word boulle which means small ball. Bullets are made of a variety of materials and they are available singly as they would be used in muzzle loading and cap and ball firearms, as part of a paper cartridge, and much more commonly as a component of metallic cartridges. Bullets are made in a numbers of styles and constructions depending on how they will be used. Many bullets have specialized functions, such as hunting, target shooting, training, defense, a bullet is not a cartridge. In paper and metallic cartridges a bullet is one component of the cartridge, bullet sizes are expressed by their weight and diameter in both English and Metric measurement systems. For example.22 caliber 55 grain bullets or 5. 56mm 55 grain bullets are the same caliber, the word bullet is often used colloquially to refer to a cartridge, which is a combination of the bullet, paper or metallic case/shell, powder, and primer. This use of bullet, when cartridge is intended, leads to confusion when the components of a cartridge are discussed or intended, the bullets used in many cartridges are fired at a muzzle velocity faster than the speed of sound. Meaning they are supersonic and thus can travel a substantial distance, bullet speed through air depends on a number of factors such as barometric pressure, humidity, air temperature, and wind speed. Subsonic cartridges fire bullets slower than the speed of sound and so there is no sonic crack and this means that a subsonic cartridge such as.45 ACP can be effectively suppressed to be substantially quieter than a supersonic cartridge such as the.223 Remington. Bullets do not normally contain explosives, but damage the target by impact. The first use of gunpowder in Europe was recorded in 1247 and it had been used in China for hundreds of years. Later in 1364 hand cannon appeared, early projectiles were made of stone. Stone was used in cannon and hand cannon, in cannon it was eventually found that stone would not penetrate stone fortifications which gave rise to the use of heavier metals for the round projectiles. Hand cannon projectiles developed in a similar following the failure of stone from siege cannon. The first recorded instance of a ball from a hand cannon penetrating armor occurred in 1425. In this photograph of shot retrieved from the wreck of the Mary Rose which was sunk in 1545, the round shot are clearly of different sizes and some are stone while others are cast iron. The development of the hand culverin and matchlock arquebus brought about the use of cast lead balls as projectiles, bullet is derived from the French word boulette, which roughly means little ball
7.
Unguided bomb
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This described all aircraft bombs in general service until the latter half of World War II, and the vast majority until the late 1980s. Then, with the increased use of precision-guided munitions, a retronym was needed to separate smart bombs from free-fall bombs. Dumb bomb was used for a time, but many military circles felt it sounded too trite, previously, they were also referred to as iron bombs. Unguided bombs typically use a contact fuse for detonation upon impact, one alternative is a fuse with an altimeter, to cause an air burst at the desired altitude. The retarded bomb uses a method of creating increased aerodynamic drag, such as a parachute, ballute. However, these bombs are less accurate than conventional free-fall bombs, generally the high-drag tail replaces the low-drag so that the same bomb can be configured for either mode of attack during weapons preparation. High-drag bombs can also be dropped in low-drag mode if the pilot selects this option in the weapon system
8.
Rocket
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A rocket is a missile, spacecraft, aircraft or other vehicle that obtains thrust from a rocket engine. Rocket engine exhaust is formed entirely from propellant carried within the rocket before use, Rocket engines work by action and reaction and push rockets forward simply by expelling their exhaust in the opposite direction at high speed, and can therefore work in the vacuum of space. In fact, rockets work more efficiently in space than in an atmosphere, multistage rockets are capable of attaining escape velocity from Earth and therefore can achieve unlimited maximum altitude. Compared with airbreathing engines, rockets are lightweight and powerful and capable of generating large accelerations. To control their flight, rockets rely on momentum, airfoils, auxiliary engines, gimballed thrust, momentum wheels, deflection of the exhaust stream, propellant flow, spin. Rockets for military and recreational uses date back to at least 13th century China, significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology for the Space Age, including setting foot on the Earths moon. Rockets are now used for fireworks, weaponry, ejection seats, launch vehicles for satellites, human spaceflight. Chemical rockets are the most common type of high power rocket, chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks, the first gunpowder-powered rockets were developed in Song China, by the 13th century. The Chinese rocket technology was adopted by the Mongols and the invention was spread via the Mongol invasions to the Near East, medieval and early modern rockets were used militarily as incendiary weapons in sieges. An early Chinese text to mention the use of rockets was the Huolongjing, between 1270 and 1280, Hasan al-Rammah wrote al-furusiyyah wa al-manasib al-harbiyya, which included 107 gunpowder recipes,22 of which are for rockets. In Europe, Konrad Kyeser described rockets in his military treatise Bellifortis around 1405. The name Rocket comes from the Italian rocchetta, meaning bobbin or little spindle, the Italian term was adopted into German in the mid 16th century by Leonhard Fronsperger and Conrad Haas, and by the early 17th century into English. Artis Magnae Artilleriae pars prima, an important early work on rocket artillery. The first iron-cased rockets were developed in the late 18th century in the Kingdom of Mysore, in 1814, Francis Scott Key wrote the line rockets red glare while held captive on a British ship that was laying siege to Fort McHenry. The first mathematical treatment of the dynamics of rocket propulsion is due to William Moore, in 1815, Alexander Dmitrievich Zasyadko constructed rocket-launching platforms, which allowed rockets to be fired in salvos, and gun-laying devices. William Hale in 1844 greatly increased the accuracy of rocket artillery, the Congreve rocket was further improved by Edward Mounier Boxer in 1865. Konstantin Tsiolkovsky first speculated on the possibility of manned spaceflight with rocket technology, robert Goddard in 1920 published proposed improvements to rocket technology in A Method of Reaching Extreme Altitudes
9.
Gun
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A gun is a normally tubular weapon or other device designed to discharge projectiles or other material. The projectile may be solid, liquid, gas or energy and may be free, as bullets and artillery shells, or captive as with Taser probes. Alternatively, acceleration via electromagnetic field generation may be employed in case the tube may be dispensed with. The first devices identified as guns appeared in China around CE1000, by the 12th century the technology was spreading through the rest of Asia, and into Europe by the 13th century. The origin of the English word gun is considered to derive from the given to a particular historical weapon. Domina Gunilda was the given to a remarkably large ballista. This name in turn may have derived from the Old Norse womans proper name Gunnhildr which combines two Norse words referring to battle, in any case the term gonne or gunne was applied to early hand-held firearms by the late 14th or early 15th century. The first device identified as a gun, a tube that used gunpowder to fire a spear. The Chinese had previously invented gunpowder in the 9th century, the earliest depiction of a gunpowder weapon is the illustration of a fire-lance on a mid-10th century silk banner from Dunhuang. The Dean Shoucheng Lu, an account of the siege of Dean in 1132, in due course, the proportion of saltpeter in the propellant was increased to maximise its explosive power. To better withstand that explosive power, the paper and bamboo of which fire-lance barrels were originally made came to be replaced by metal, and to take full advantage of that power, the shrapnel came to be replaced by projectiles whose size and shape filled the barrel more closely. English Privy Wardrobe accounts list ribaldis, a type of cannon, in the 1340s, the earliest surviving firearm in Europe has been found from Otepää, Estonia and it dates to at least 1396. Around the late 14th century in Europe, smaller and portable hand-held cannons were developed, in the late 15th century the Ottoman empire used firearms as part of its regular infantry. The first successful rapid-fire firearm is the Gatling Gun, invented by Richard Gatling, the worlds first sub-machine gun able to be maneuvered by a single soldier is the MP18.1, invented by Theodor Bergmann. It was introduced into service in 1918 by the German Army during World War I as the weapon of the Stosstruppen. The first assault rifle was introduced during World War II by the Germans and it was the first firearm which bridges the gap between long range rifles, machine guns, and short range sub-machine guns. Since the mid-20th century guns that fire beams of energy rather than solid projectiles have been developed, most guns use compressed gas confined by the barrel to propel the bullet up to high speed, though devices operating in other ways are sometimes called guns. In firearms the high-pressure gas is generated by combustion, usually of gunpowder and this principle is similar to that of internal combustion engines, except that the bullet leaves the barrel, while the piston transfers its motion to other parts and returns down the cylinder
10.
Propelling nozzle
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A propelling nozzle converts a gas turbine or gas generator into a jet engine. Energy available in the gas turbine exhaust is converted into a high speed propelling jet by the nozzle, turbofan engines may have an additional and separate propelling nozzle which produces a high speed propelling jet from the energy in the air that has passed through the fan. In addition, the nozzle helps to determine how the gas generator, the internal shape may be convergent or convergent-divergent. C-D nozzles can accelerate the jet to supersonic velocities within the divergent section, when afterburning engines are equipped with a C-D nozzle the throat area is variable. Nozzles for supersonic speeds, at which high nozzle pressure ratios are generated. The role of the nozzle in back-pressuring the engine is explained below, the energy to accelerate the stream comes from the temperature and pressure of the gas. The gas expands adiabatically with low losses and hence high efficiency, the gas accelerates to a final exit velocity which depends on the pressure and temperature at entry to the nozzle, the ambient pressure it exhausts to, and the efficiency of the expansion. The efficiency is a measure of the due to friction. Airbreathing engines create forward thrust on the airframe by imparting a net momentum to the air by producing a jet of exhaust gas which has a speed that exceeds that of the aircraft. The jet may or may not be expanded as described in section Reasons for C-D nozzle underexpansion. On some engines that are equipped with an afterburner the nozzle area is also varied during non-afterburning or dry thrust conditions, typically the nozzle is fully open for starting and at idle. It may then close down as the thrust lever is advanced reaching its minimum area before or at the Military or max dry thrust setting, two examples of this control are the General Electric J-79 and the Tumansky RD-22 in the MIG-29. Reasons for varying the area are explained in section Nozzle area control during dry operation. Convergent nozzles are used on jet engines. Although jet momentum still produces much of the gross thrust, the imbalance between the static pressure and atmospheric pressure still generates some thrust. The supersonic speed of the air flowing into a scramjet allows the use of a simple divergent nozzle, engines capable of supersonic flight have convergent-divergent exhaust duct features to generate supersonic flow. Rocket engines — the extreme case — owe their shape to the very high area ratios of their nozzles. This reduces the thrust producing efficiency of the nozzle by causing much of the expansion to take place downstream of the nozzle itself, consequently, rocket engines and jet engines for supersonic flight incorporate a C-D nozzle which permits further expansion against the inside of the nozzle
11.
Rifling
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In firearms, rifling consists of helical grooves in the internal surface of a guns barrel, which impart a spin to a projectile around its long axis. This spin serves to stabilize the projectile, improving its aerodynamic stability. Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one revolution, such as 1 turn in 10 inches. A shorter distance indicates a faster twist, meaning that for a given velocity the projectile will be rotating at a spin rate. Barrels intended for long, small-diameter bullets, such as the ultra-low-drag, 80-grain 0.223 inch bullets, extremely long projectiles such as flechettes may require high twist rates, these projectiles must be inherently stable, and are often fired from a smoothbore barrel. Muskets were smoothbore, large caliber weapons using ball-shaped ammunition fired at low velocity. Due to the high cost and great difficulty of manufacturing, and the need to load readily from the muzzle. Consequently, on firing the ball bounced off the sides of the barrel when fired, barrel rifling was invented in Augsburg, Germany in 1498. In 1520 August Kotter, an armourer of Nuremberg, Germany improved upon this work, though true rifling dates from the mid-16th century, it did not become commonplace until the nineteenth century. The most successful weapons using rifling with black powder were breech loaders such as the Queen Anne pistol, the grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling, a throwback to the earliest types of rifling, has become popular, polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities and greater accuracy, polygonal rifling is currently seen on pistols from CZ, Heckler & Koch, Glock, Tanfoglio, and Kahr Arms, as well as the Desert Eagle. Such guns have achieved significant increases in velocity and range. Examples include the South African G5 and the German PzH2000, gain-twist rifling begins with very little change in the projectiles angular momentum during the first few inches of bullet travel after ignition during the transition from chamber to throat. This enables the bullet to remain undisturbed and trued to the case mouth. After engaging the rifling the bullet is progressively subjected to accelerated angular momentum as burning powder propels it down the barrel. By only gradually increasing the rate, torque is spread along a much longer section of barrel. Gain-twist rifling was used as early as the American Civil War, colt Army and Navy revolvers both employed gain-twist rifling
12.
Gun barrel
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A gun barrel is a part of firearms and artillery pieces. The hollow interior of the barrel is called the bore, a gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the projectile as it is being pushed out by the expanding gas. Modern small arms barrels are made of known and tested to withstand the pressures involved. Artillery pieces are made by various techniques providing reliably sufficient strength, early firearms were muzzle-loading, with powder, and then shot loaded from the muzzle, capable of only a low rate of fire. During the 19th century effective mechanical locks were invented that sealed a breech-loading weapon against the escape of propellant gases, the early Chinese, the inventors of gunpowder, used bamboo, a naturally tubular stalk, as the first barrels in gunpowder projectile weapons. Early European guns were made of iron, usually with several strengthening bands of the metal wrapped around circular wrought iron rings. The Chinese were the first to master cast-iron cannon barrels, early cannon barrels were very thick for their caliber. Bore evacuator Bore snake Cannon Muzzle Polygonal rifling Rifling Slug barrel Smoothbore
13.
Gravity
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Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets, stars and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research. While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible
14.
Ballistic missile
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A ballistic missile is a missile that follows a ballistic trajectory with the objective of delivering one or more warheads to a predetermined target. A ballistic missile is only guided during relatively brief periods of flight and this contrasts to a cruise missile, which is aerodynamically guided in powered flight. Long range intercontinental ballistic missiles are launched on a flight trajectory. Shorter range ballistic missiles stay within the Earths atmosphere, the earliest use of rockets as a weapon date to the 13th Century. A pioneer ballistic missile was the A-4, commonly known as the V-2 rocket developed by Nazi Germany in the 1930s and 1940s under the direction of Wernher von Braun. The first successful launch of a V-2 was on October 3,1942, by the end of World War II in May 1945, over 3,000 V-2s had been launched. The R-7 Semyorka was the first intercontinental ballistic missile, a total of 30 nations have deployed operational ballistic missiles. Development continues with around 100 ballistic missile tests in 2007, mostly by China, Iran. In 2010, the U. S. and Russian governments signed a treaty to reduce their inventory of intercontinental ballistic missiles over a period to 1550 units each. Ballistic missiles can be launched from fixed sites or mobile launchers, including vehicles, aircraft, ships, the powered flight portion can last from a few tenths of seconds to several minutes and can consist of multiple rocket stages. When in space and no more thrust is provided, the missile enters free-flight, the re-entry stage begins at an altitude where atmospheric drag plays a significant part in missile trajectory, and lasts until missile impact. The course taken by ballistic missiles has two significant desirable properties, first, ballistic missiles that fly above the atmosphere have a much longer range than would be possible for cruise missiles of the same size. Powered rocket flight through thousands of kilometers of air would require greater amounts of fuel, making the launch vehicles larger and easier to detect. Powered missiles that can cover similar ranges, such as missiles, do not use rocket motors for the majority of their flight. Despite this, cruise missiles have not made ballistic missiles obsolete, due to the major advantage. An ICBM can strike a target within a 10,000 km range in about 30 to 35 minutes, with terminal speeds of over 5,000 m/s, ballistic missiles are much harder to intercept than cruise missiles, due to the much shorter time available to intercept them. This is why ballistic missiles are some of the most feared weapons available, despite the fact that cruise missiles are cheaper, more mobile, Ballistic missiles can vary widely in range and use, and are often divided into categories based on range. A comparable missile would be the decommissioned Chinas JL-1 SLBM with a range of less than 2, tactical, short- and medium-range missiles are often collectively referred to as tactical and theatre ballistic missiles, respectively
15.
Missile
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In modern language, a missile is a self-propelled precision-guided munition system, as opposed to an unguided self-propelled munition, referred to as a rocket. Missiles have four components, targeting and/or missile guidance, flight system, engine. Missiles come in types adapted for different purposes, surface-to-surface and air-to-surface missiles, surface-to-air missiles, air-to-air missiles, all known existing missiles are designed to be propelled during powered flight by chemical reactions inside a rocket engine, jet engine, or other type of engine. Non-self-propelled airborne explosive devices are referred to as shells and usually have a shorter range than missiles. In ordinary British-English usage predating guided weapons, a missile is any thrown object, the word missile comes from the Latin verb mittere, meaning to send. In military usage, munitions projected towards a target are broadly categorised as follows, a powered, unguided munition is known as a rocket. Unpowered munitions not fired from a gun are called bombs whether guided or not, munitions that are fired from a gun are known as projectiles whether guided or not. If explosive, they are more specifically as shells or mortar bombs. Powered munitions that travel through water are called torpedoes, hand grenades are not usually classed as missiles. The first missiles to be used operationally were a series of missiles developed by Nazi Germany in World War II, most famous of these are the V-1 flying bomb and V-2 rocket, both of which used a simple mechanical autopilot to keep the missile flying along a pre-chosen route. Less well known were a series of anti-shipping and anti-aircraft missiles, however, these early systems in World War II were only built in small numbers. Guided missiles have a number of different system components, Targeting and/or missile guidance Flight system Engine Warhead Missiles may be targeted in a number of ways. The most common method is to use some form of radiation, such as infrared, lasers or radio waves and this radiation may emanate from the target, it may be provided by the missile itself, or it may be provided by a friendly third party. The first two are known as fire-and-forget as they need no further support or control from the launch vehicle/platform in order to function. Another method is to use a TV guidance—using either visible light or infrared—in order to see the target, the picture may be used either by a human operator who steers the missile onto its target or by a computer doing much the same job. One of the more bizarre guidance methods instead used a pigeon to steer the missile to its target, many missiles use a combination of two or more of the above methods to improve accuracy and the chances of a successful engagement. Another method is to target the missile by knowing the location of the target and using a system such as INS. This guidance system guides the missile by knowing the current position and the position of the target
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Trajectory
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A trajectory or flight path is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example, it can be an orbit—the path of a planet, an asteroid, or a comet as it travels around a central mass. A trajectory can be described either by the geometry of the path or as the position of the object over time. In control theory a trajectory is a set of states of a dynamical system. In discrete mathematics, a trajectory is a sequence k ∈ N of values calculated by the application of a mapping f to an element x of its source. A familiar example of a trajectory is the path of a projectile, in a significantly simplified model, the object moves only under the influence of a uniform gravitational force field. This can be an approximation for a rock that is thrown for short distances. In this simple approximation, the trajectory takes the shape of a parabola, generally when determining trajectories, it may be necessary to account for nonuniform gravitational forces and air resistance. This is the focus of the discipline of ballistics, one of the remarkable achievements of Newtonian mechanics was the derivation of the laws of Kepler. In the gravitational field of a point mass or an extended mass. Newtons theory later developed into the branch of physics known as classical mechanics. It employs the mathematics of differential calculus, over the centuries, countless scientists have contributed to the development of these two disciplines. Classical mechanics became a most prominent demonstration of the power of thought, i. e. reason. It helps to understand and predict an enormous range of phenomena, trajectories are, consider a particle of mass m, moving in a potential field V. Physically speaking, mass represents inertia, and the field V represents external forces of a kind known as conservative. Given V at every relevant position, there is a way to infer the associated force that would act at that position, not all forces can be expressed in this way, however. The motion of the particle is described by the differential equation m d 2 x → d t 2 = − ∇ V with x → =. On the right-hand side, the force is given in terms of ∇ V and this is the mathematical form of Newtons second law of motion, force equals mass times acceleration, for such situations
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Classical mechanics
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In physics, classical mechanics is one of the two major sub-fields of mechanics, along with quantum mechanics. Classical mechanics is concerned with the set of physical laws describing the motion of bodies under the influence of a system of forces. The study of the motion of bodies is an ancient one, making classical mechanics one of the oldest and largest subjects in science, engineering and technology. Classical mechanics describes the motion of objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars. Within classical mechanics are fields of study that describe the behavior of solids, liquids and gases, Classical mechanics also provides extremely accurate results as long as the domain of study is restricted to large objects and the speeds involved do not approach the speed of light. When both quantum and classical mechanics cannot apply, such as at the level with high speeds. Since these aspects of physics were developed long before the emergence of quantum physics and relativity, however, a number of modern sources do include relativistic mechanics, which in their view represents classical mechanics in its most developed and accurate form. Later, more abstract and general methods were developed, leading to reformulations of classical mechanics known as Lagrangian mechanics and these advances were largely made in the 18th and 19th centuries, and they extend substantially beyond Newtons work, particularly through their use of analytical mechanics. The following introduces the concepts of classical mechanics. For simplicity, it often models real-world objects as point particles, the motion of a point particle is characterized by a small number of parameters, its position, mass, and the forces applied to it. Each of these parameters is discussed in turn, in reality, the kind of objects that classical mechanics can describe always have a non-zero size. Objects with non-zero size have more complicated behavior than hypothetical point particles, because of the degrees of freedom. However, the results for point particles can be used to such objects by treating them as composite objects. The center of mass of a composite object behaves like a point particle, Classical mechanics uses common-sense notions of how matter and forces exist and interact. It assumes that matter and energy have definite, knowable attributes such as where an object is in space, non-relativistic mechanics also assumes that forces act instantaneously. The position of a point particle is defined with respect to a fixed reference point in space called the origin O, in space. A simple coordinate system might describe the position of a point P by means of a designated as r. In general, the point particle need not be stationary relative to O, such that r is a function of t, the time
18.
Cruise missile
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A cruise missile is a guided missile used against terrestrial targets that remains in the atmosphere and flies the major portion of its flight path at approximately constant speed. Cruise missiles are designed to deliver a warhead over long distances with high precision. Modern cruise missiles are capable of travelling at supersonic or high speeds, are self-navigating. The idea of a torpedo was shown in the British 1909 film The Airship Destroyer. In 1916, Lawrence Sperry built and patented an aerial torpedo, a small biplane carrying a TNT charge, a Sperry autopilot, inspired by these experiments, the United States Army developed a similar flying bomb called the Kettering Bug. Germany had also flown trials with remote-controlled aerial gliders built by Siemens-Schuckert beginning in 1916, in the period between the World Wars the United Kingdom developed the Larynx, which underwent a few flight tests in the 1920s. In the Soviet Union, Sergei Korolev headed the GIRD-06 cruise missile project from 1932 to 1939, the 06/III and 06/IV contained gyroscopic guidance systems. The vehicle was designed to boost to 28 km altitude and glide a distance of 280 km, in 1944, Germany deployed the first operational cruise missiles in World War II. The V-1, often called a bomb, contained a gyroscope guidance system and was propelled by a simple pulsejet engine. Accuracy was sufficient only for use against very large targets, while the range of 250 km was significantly lower than that of a bomber carrying the same payload, the main advantages were speed and expendability. The production cost of a V-1 was only a fraction of that of a V-2 supersonic ballistic missile. Unlike the V-2, however, the deployments of the V-1 required stationary launch ramps which were susceptible to bombardment. Immediately after the war the United States Air Force had 21 different guided missile projects, all were cancelled by 1948, except four — the Air Materiel Command BANSHEE, the SM-62 Snark, the SM-64 Navaho, and the MGM-1 Matador. The BANSHEE design was similar to Operation Aphrodite, like Aphrodite, it failed, during the Cold War period both the United States and the Soviet Union experimented further with the concept, deploying early cruise missiles from land, submarines and aircraft. The main outcome of the United States Navy submarine missile project was the SSM-N-8 Regulus missile, the United States Air Forces first operational surface-to-surface missile was the winged, mobile, nuclear-capable MGM-1 Matador, also similar in concept to the V-1. Deployment overseas began in 1954, first to West Germany and later to the Republic of China and this alert was in response to the crisis posed by the Soviet attack on Hungary which suppressed the Hungarian Revolution of 1956. Between 1957 and 1961 the United States followed an ambitious and well-funded program to develop a nuclear-powered cruise missile and it was designed to fly below the enemys radar at speeds above Mach 3 and carry a number of hydrogen bombs that it would drop along its path over enemy territory. Although the concept was sound and the 500 megawatt engine finished a successful test run in 1961
19.
Aerodynamics
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Aerodynamics, from Greek ἀήρ aer + δυναμική, the study of the motion of air, particularly its interaction with a solid object, such as an airplane wing. Aerodynamics is a sub-field of fluid dynamics and gas dynamics, the term aerodynamics is often used synonymously with gas dynamics, the difference being that gas dynamics applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the sense in the eighteenth century. Most of the efforts in aerodynamics were directed toward achieving heavier-than-air flight. Recent work in aerodynamics has focused on issues related to flow, turbulence. Fundamental concepts of continuum, drag, and pressure gradients appear in the work of Aristotle, in 1726, Sir Isaac Newton became the first person to develop a theory of air resistance, making him one of the first aerodynamicists. In 1757, Leonhard Euler published the more general Euler equations which could be applied to both compressible and incompressible flows, the Euler equations were extended to incorporate the effects of viscosity in the first half of the 1800s, resulting in the Navier-Stokes equations. The Navier-Stokes equations are the most general governing equations of fluid flow, in 1871, Francis Herbert Wenham constructed the first wind tunnel, allowing precise measurements of aerodynamic forces. Drag theories were developed by Jean le Rond dAlembert, Gustav Kirchhoff, in 1889, Charles Renard, a French aeronautical engineer, became the first person to reasonably predict the power needed for sustained flight. Otto Lilienthal, the first person to become successful with glider flights, was also the first to propose thin, curved airfoils that would produce high lift. Building on these developments as well as carried out in their own wind tunnel. During the time of the first flights, Frederick W. Lanchester, Martin Wilhelm Kutta, Kutta and Zhukovsky went on to develop a two-dimensional wing theory. Expanding upon the work of Lanchester, Ludwig Prandtl is credited with developing the mathematics behind thin-airfoil, as aircraft speed increased, designers began to encounter challenges associated with air compressibility at speeds near or greater than the speed of sound. The differences in air flows under such conditions leds to problems in control, increased drag due to shock waves. The ratio of the speed to the speed of sound was named the Mach number after Ernst Mach who was one of the first to investigate the properties of supersonic flow. Theodore von Kármán and Hugh Latimer Dryden introduced the term transonic to describe flow speeds around Mach 1 where drag increases rapidly, by the time the sound barrier was broken, aerodynamicists understanding of the subsonic and low supersonic flow had matured. The Cold War prompted the design of an line of high performance aircraft. Understanding the motion of air around an object enables the calculation of forces, in many aerodynamics problems, the forces of interest are the fundamental forces of flight, lift, drag, thrust, and weight
20.
Throwing stick
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The throwing stick or throwing club is one of the first weapons used by early humans and cultures all around the world. In essence, it is a stave or wooden club thrown as a projectile to hunt small game such as rabbits or waterfowl, in flight, it rotates rapidly, hitting the target with one of the ends, maiming or killing it. One difference between a stick and a javelin is in their shapes and lengths. A javelin is almost always a straight shaft with either a pointed tip or an attached to the front end. A throwing stick can be straight like a wooden shaft or curved like the boomerang. It became obsolete as slings and bows became more prevalent, except for on the Australian continent, Throwing sticks shaped like returning boomerangs are designed to fly straight to a target at long ranges. Their surfaces are shaped as airfoils, when tuned correctly they do not exhibit curved flight, but rather they fly on an extended straight flight path. Straight flight ranges greater than 100 meters distance have been reported by sources as well as in recent research. There were some throwing sticks placed in the tombs of pharaohs, the throwing stick is a tool used in hunting small game and waterfowl. The Ancient Egyptians used throwing sticks to hunt ducks, as seen in wall paintings. The 18th dynasty Pharaoh Tutankhamun was a lover of duck hunting. Menceys, the kings of the ancient Guanches of the Canary Islands, the Aborigines of Australia used the boomerang. Its range was in excess of 100 meters and it could also be wielded as a club or knife for attacking close kangaroo, wallaby, and emu by using it as a club. Some Native American tribes such as the Hopi, as well as all southern California tribes, utilized the throwing stick to hunt rabbits, other titles for the throwing stick are, rabbit stick, throwing club, killer stick, baton, boomerang, and kylie. The throwing stick can also be used as a weapon in human combat, as a survival tool, the throwing stick is one of the most effective and easiest tools to obtain. Other than a weapon, it can also be used as a tool for making fire-pits. A curved limb will suffice as a throwing stick, Ancient throwing sticks were made of hardwood with a weighted or curved end to one side to impart momentum so the stick stays straight and does not wobble in mid-flight. Some throwing sticks and their variations are about 2 to 3 feet long pieces of thick hardwood, when they are thrown, they spin, creating the image of a sort of blurry disc
21.
Spear-thrower
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A spear-thrower or atlatl is a tool that uses leverage to achieve greater velocity in dart-throwing, and includes a bearing surface which allows the user to store energy during the throw. It may consist of a shaft with a cup or a spur at the end that supports, the spear-thrower is held in one hand, gripped near the end farthest from the cup. The dart is thrown by the action of the upper arm, the throwing arm together with the atlatl acts as a lever. The spear-thrower is a low-mass, fast-moving extension of the throwing arm and this extra length allows the thrower to impart force to the dart over a longer distance, thus imparting more energy and ultimately higher speeds. Common modern ball throwers use the same principle, a spear-thrower is a long-range weapon and can readily impart to a projectile speeds of over 150 km/h. In the United States the Nahuatl word atlatl is often used for revived uses of spear-throwers, the ancient Greeks and Romans used a leather thong or loop, known as an ankule or amentum, as a spear-throwing device. Spear-thrower designs may include such as thong loops to fit the fingers, the use of flexible shafts, stone balance weights. Darts resemble large arrows or thin spears and are typically from 1.2 to 2.7 m in length and 9 to 16 mm in diameter, another important improvement to the spear-throwers design was the introduction of a small weight strapped to its midsection. Some atlatlists maintain that stone weights add mass to the shaft of the device, causing resistance to acceleration when swung and resulting in a more forceful, others claim that spear-thrower weights add only stability to a cast, resulting in greater accuracy. Based on previous work done by William S. Webb, William R, the use of the device would reduce the telltale zip of a swung atlatl to a more subtle woof sound that did not travel as far and was less likely to alert prey. The woomera design is different from most other spear-throwers, in that it has a curved, hollow shape. Several Stone Age spear-throwers are decorated with carvings of animals, the British Museum has a mammoth, many pieces of decorated bone may have belonged to Bâtons de commandement. The Aztec atlatl was often decorated with designs and feathers. Wooden darts were known at least since the Middle Paleolithic, while the spear-thrower is capable of casting a dart well over one hundred meters, it is most accurately used at distances of twenty meters or less. The spearthrower is believed to have been in use by Homo sapiens since the Upper Paleolithic, most stratified European finds come from the Magdalenian. In this period, elaborate pieces, often in the form of animals, are common, the earliest secure data concerning atlatls have come from several caves in France dating to the Upper Paleolithic, about 21,000 to 17,000 years ago. The earliest known example is a 17, 500-year-old Solutrean atlatl made of antler, found at Combe Saunière. In Europe, the spear-thrower was supplemented by the bow and arrow in the Epi-Paleolithic and this allowed for more forgiving flint knapping, dart heads designed for a particular spear thrower tend to differ in mass by only a few percent
22.
South Africa
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South Africa, officially the Republic of South Africa, is the southernmost country in Africa. South Africa is the 25th-largest country in the world by land area and it is the southernmost country on the mainland of the Old World or the Eastern Hemisphere. About 80 percent of South Africans are of Sub-Saharan African ancestry, divided among a variety of ethnic groups speaking different Bantu languages, the remaining population consists of Africas largest communities of European, Asian, and multiracial ancestry. South Africa is a multiethnic society encompassing a variety of cultures, languages. Its pluralistic makeup is reflected in the recognition of 11 official languages. The country is one of the few in Africa never to have had a coup détat, however, the vast majority of black South Africans were not enfranchised until 1994. During the 20th century, the black majority sought to recover its rights from the dominant white minority, with this struggle playing a role in the countrys recent history. The National Party imposed apartheid in 1948, institutionalising previous racial segregation, since 1994, all ethnic and linguistic groups have held political representation in the countrys democracy, which comprises a parliamentary republic and nine provinces. South Africa is often referred to as the Rainbow Nation to describe the multicultural diversity. The World Bank classifies South Africa as an economy. Its economy is the second-largest in Africa, and the 34th-largest in the world, in terms of purchasing power parity, South Africa has the seventh-highest per capita income in Africa. However, poverty and inequality remain widespread, with about a quarter of the population unemployed, nevertheless, South Africa has been identified as a middle power in international affairs, and maintains significant regional influence. The name South Africa is derived from the geographic location at the southern tip of Africa. Upon formation the country was named the Union of South Africa in English, since 1961 the long form name in English has been the Republic of South Africa. In Dutch the country was named Republiek van Zuid-Afrika, replaced in 1983 by the Afrikaans Republiek van Suid-Afrika, since 1994 the Republic has had an official name in each of its 11 official languages. Mzansi, derived from the Xhosa noun umzantsi meaning south, is a name for South Africa. South Africa contains some of the oldest archaeological and human fossil sites in the world, extensive fossil remains have been recovered from a series of caves in Gauteng Province. The area is a UNESCO World Heritage site and has termed the Cradle of Humankind
23.
Hamburg
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Hamburg, officially Freie und Hansestadt Hamburg, is the second largest city in Germany and the eighth largest city in the European Union. It is the second smallest German state by area and its population is over 1.7 million people, and the wider Hamburg Metropolitan Region covers more than 5.1 million inhabitants. The city is situated on the river Elbe, the official long name reflects Hamburgs history as a member of the medieval Hanseatic League, a free imperial city of the Holy Roman Empire, a city-state, and one of the 16 states of Germany. Before the 1871 Unification of Germany, it was a sovereign state. Prior to the changes in 1919, the civic republic was ruled by a class of hereditary grand burghers or Hanseaten. Though repeatedly destroyed by the Great Fire of Hamburg, the floods and military conflicts including WW2 bombing raids, the city managed to recover and emerge wealthier after each catastrophe. On the river Elbe, Hamburg is a port and a global service, media, logistics and industrial hub, with headquarters and facilities of Airbus, Blohm + Voss, Aurubis, Beiersdorf. The radio and television broadcaster NDR, Europes largest printing and publishing firm Gruner + Jahr, Hamburg has been an important financial centre for centuries, and is the seat of Germanys oldest stock exchange and the worlds second oldest bank, Berenberg Bank. The city is a fast expanding tourist destination for domestic and international visitors. It ranked 16th in the world for livability in 2015, the ensemble Speicherstadt and Kontorhausviertel was declared a World Heritage Site by the UNESCO in 2015. Hamburg is a major European science, research and education hub with several universities and institutes and its creative industries and major cultural venues include the renowned Elbphilharmonie and Laeisz concert halls, various art venues, music producers and artists. It is regarded as a haven for artists, gave birth to movements like Hamburger Schule. Hamburg is also known for theatres and a variety of musical shows. St. Paulis Reeperbahn is among the best known European entertainment districts, Hamburg is on the southern point of the Jutland Peninsula, between Continental Europe to the south and Scandinavia to the north, with the North Sea to the west and the Baltic Sea to the north-east. It is on the River Elbe at its confluence with the Alster, the city centre is around the Binnenalster and Außenalster, both formed by damming the River Alster to create lakes. The island of Neuwerk and two neighbouring islands Scharhörn and Nigehörn, in the Hamburg Wadden Sea National Park, are also part of Hamburg. The neighbourhoods of Neuenfelde, Cranz, Francop and Finkenwerder are part of the Altes Land region, neugraben-Fischbek has Hamburgs highest elevation, the Hasselbrack at 116.2 metres AMSL. Hamburg has a climate, influenced by its proximity to the coast
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History of China
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Written records of the history of China can be found from as early as 1500 BC under the Shang dynasty. Ancient historical texts such as the Records of the Grand Historian and the Bamboo Annals describe a Xia dynasty, with thousands of years of continuous history, China is one of the worlds oldest civilizations, and is regarded as one of the cradles of civilization. Much of Chinese culture, literature and philosophy developed during the Zhou dynasty. This is one of multiple periods of failed statehood in Chinese history, between eras of multiple kingdoms and warlordism, Chinese dynasties have ruled parts or all of China, in some eras control stretched as far as Xinjiang and Tibet, as at present. In 221 BC Qin Shi Huang united the warring kingdoms and created for himself the title of emperor of the Qin dynasty. Successive dynasties developed bureaucratic systems that enabled the emperor to control vast territories directly, in the 21 centuries from 206 BC until AD1912, routine administrative tasks were handled by a special elite, the Scholar-officials. Young men were selected through difficult examinations and were well-versed in calligraphy and philosophy. What is now China was inhabited by Homo erectus more than a million years ago, recent study shows that the stone tools found at Xiaochangliang site are magnetostratigraphically dated to 1.36 million years ago. The archaeological site of Xihoudu in Shanxi Province is the earliest recorded use of fire by Homo erectus, the excavations at Yuanmou and later Lantian show early habitation. Perhaps the most famous specimen of Homo erectus found in China is the so-called Peking Man discovered in 1923–27, fossilised teeth of Homo sapiens dating to 125, 000–80,000 BC have been discovered in Fuyan Cave in Dao County in Hunan. The Neolithic age in China can be traced back to about 10,000 BC, Early evidence for proto-Chinese millet agriculture is radiocarbon-dated to about 7000 BC. The earliest evidence of cultivated rice, found by the Yangtze River, is carbon-dated to 8,000 years ago, farming gave rise to the Jiahu culture. At Damaidi in Ningxia,3,172 cliff carvings dating to 6000–5000 BC have been discovered, featuring 8,453 individual characters such as the sun, moon, stars, gods and these pictographs are reputed to be similar to the earliest characters confirmed to be written Chinese. Chinese proto-writing existed in Jiahu around 7000 BC, Dadiwan from 5800 BC to 5400 BC, Damaidi around 6000 BC, some scholars have suggested that Jiahu symbols were the earliest Chinese writing system. With agriculture came increased population, the ability to store and redistribute crops, Later, Yangshao culture was superseded by the Longshan culture, which was also centered on the Yellow River from about 3000 BC to 2000 BC. Bronze artifacts have been found at the Majiayao culture site, The Bronze Age is also represented at the Lower Xiajiadian culture site in northeast China. Sanxingdui located in what is now Sichuan province is believed to be the site of a ancient city. The site was first discovered in 1929 and then re-discovered in 1986, Chinese archaeologists have identified the Sanxingdui culture to be part of the ancient kingdom of Shu, linking the artifacts found at the site to its early legendary kings
25.
Galileo Galilei
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Galileo Galilei was an Italian polymath, astronomer, physicist, engineer, philosopher, and mathematician. He played a role in the scientific revolution of the seventeenth century. Galileo also worked in applied science and technology, inventing an improved military compass, Galileos championing of heliocentrism and Copernicanism was controversial during his lifetime, when most subscribed to either geocentrism or the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism because of the absence of a stellar parallax. He was tried by the Inquisition, found vehemently suspect of heresy and he spent the rest of his life under house arrest. He has been called the father of observational astronomy, the father of modern physics, the father of scientific method, and the father of science. Galileo was born in Pisa, Italy, on 15 February 1564, the first of six children of Vincenzo Galilei, a famous lutenist, composer, and music theorist, and Giulia, three of Galileos five siblings survived infancy. The youngest, Michelangelo, also became a noted lutenist and composer although he contributed to financial burdens during Galileos young adulthood, Michelangelo was unable to contribute his fair share of their fathers promised dowries to their brothers-in-law, who would later attempt to seek legal remedies for payments due. Michelangelo would also occasionally have to borrow funds from Galileo to support his musical endeavours and these financial burdens may have contributed to Galileos early fire to develop inventions that would bring him additional income. When Galileo Galilei was eight, his family moved to Florence and he then was educated in the Vallombrosa Abbey, about 30 km southeast of Florence. Galileo Bonaiuti was buried in the church, the Basilica of Santa Croce in Florence. It was common for mid-sixteenth century Tuscan families to name the eldest son after the parents surname, hence, Galileo Galilei was not necessarily named after his ancestor Galileo Bonaiuti. The Italian male given name Galileo derives from the Latin Galilaeus, meaning of Galilee, the biblical roots of Galileos name and surname were to become the subject of a famous pun. In 1614, during the Galileo affair, one of Galileos opponents, in it he made a point of quoting Acts 1,11, Ye men of Galilee, why stand ye gazing up into heaven. Despite being a genuinely pious Roman Catholic, Galileo fathered three children out of wedlock with Marina Gamba and they had two daughters, Virginia and Livia, and a son, Vincenzo. Their only worthy alternative was the religious life, both girls were accepted by the convent of San Matteo in Arcetri and remained there for the rest of their lives. Virginia took the name Maria Celeste upon entering the convent and she died on 2 April 1634, and is buried with Galileo at the Basilica of Santa Croce, Florence. Livia took the name Sister Arcangela and was ill for most of her life, Vincenzo was later legitimised as the legal heir of Galileo and married Sestilia Bocchineri
26.
Projectile motion
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A special case of a ballistic trajectory for a rocket is a lofted trajectory, a trajectory with an apogee greater than the minimum-energy trajectory to the same range. In other words, the rocket higher and by doing so it uses more energy to get to the same landing point. This may be done for reasons such as increasing distance to the horizon to give greater viewing/communication range or for changing the angle with which a missile will impact on landing. Lofted trajectories are sometimes used in both missile rocketry and in spaceflight, the following applies for ranges which are small compared to the size of the Earth. For longer ranges see sub-orbital spaceflight, in the equations on this page, the following variables will be used, g, the gravitational acceleration—usually taken to be 9. A ballistic missile is a missile only guided during the brief initial powered phase of flight. These formulae ignore aerodynamic drag and also assume that the area is at uniform height 0. This distance is, d = v 2 g For explicit derivations of these results, the time of flight is the time it takes for the projectile to finish its trajectory. The above results are found in Range of a projectile, the third term is the deviation from traveling in a straight line. The magnitude, | v |, of the velocity of the projectile at distance x is given by | v | = v 2 −2 g x tan θ +2. The magnitude |v| of the velocity is given by | v | = V x 2 + V y 2, here the x-velocity remains constant, it is always equal to v cos θ. The y-velocity can be using the formula v f = v i + a t by setting vi = v sin θ, a = -g. Then, V y = v sin θ − g x v cos θ and | v | =2 +2, the formula above is found by simplifying. This formula allows one to find the angle of launch needed without the restriction of y =0, the tangent of the angle of elevation is proportional to the time since the ball was sent into the air, usually by being struck with a bat. Even when the ball is really descending, near the end of its flight, the player therefore sees it in line with a point ascending vertically from the batsman at constant speed. Finding the place from which the ball appears to rise steadily helps the player to position himself correctly to make the catch, if he is too close to the batsman who has hit the ball, it will appear to rise at an accelerating rate. If he is too far from the batsman, it appear to slow rapidly. Proof Suppose the ball starts with a component of velocity of v y upward
27.
Isaac Newton
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His book Philosophiæ Naturalis Principia Mathematica, first published in 1687, laid the foundations of classical mechanics. Newton also made contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz for developing the infinitesimal calculus. Newtons Principia formulated the laws of motion and universal gravitation that dominated scientists view of the universe for the next three centuries. Newtons work on light was collected in his influential book Opticks. He also formulated a law of cooling, made the first theoretical calculation of the speed of sound. Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge, politically and personally tied to the Whig party, Newton served two brief terms as Member of Parliament for the University of Cambridge, in 1689–90 and 1701–02. He was knighted by Queen Anne in 1705 and he spent the last three decades of his life in London, serving as Warden and Master of the Royal Mint and his father, also named Isaac Newton, had died three months before. Born prematurely, he was a child, his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug. When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabas Smith, leaving her son in the care of his maternal grandmother, Newtons mother had three children from her second marriage. From the age of twelve until he was seventeen, Newton was educated at The Kings School, Grantham which taught Latin and Greek. He was removed from school, and by October 1659, he was to be found at Woolsthorpe-by-Colsterworth, Henry Stokes, master at the Kings School, persuaded his mother to send him back to school so that he might complete his education. Motivated partly by a desire for revenge against a bully, he became the top-ranked student. In June 1661, he was admitted to Trinity College, Cambridge and he started as a subsizar—paying his way by performing valets duties—until he was awarded a scholarship in 1664, which guaranteed him four more years until he would get his M. A. He set down in his notebook a series of Quaestiones about mechanical philosophy as he found it, in 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became calculus. Soon after Newton had obtained his B. A. degree in August 1665, in April 1667, he returned to Cambridge and in October was elected as a fellow of Trinity. Fellows were required to become ordained priests, although this was not enforced in the restoration years, however, by 1675 the issue could not be avoided and by then his unconventional views stood in the way. Nevertheless, Newton managed to avoid it by means of a special permission from Charles II. A and he was elected a Fellow of the Royal Society in 1672. Newtons work has been said to distinctly advance every branch of mathematics then studied and his work on the subject usually referred to as fluxions or calculus, seen in a manuscript of October 1666, is now published among Newtons mathematical papers
28.
Ancient Greek
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Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Aeolic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are also several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the later Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians, Aeolians, and Ionians, each with their own defining and distinctive dialects. Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
29.
Space
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Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Physical space is conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. The concept of space is considered to be of importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Many of these classical philosophical questions were discussed in the Renaissance and then reformulated in the 17th century, in Isaac Newtons view, space was absolute—in the sense that it existed permanently and independently of whether there was any matter in the space. Other natural philosophers, notably Gottfried Leibniz, thought instead that space was in fact a collection of relations between objects, given by their distance and direction from one another. In the 18th century, the philosopher and theologian George Berkeley attempted to refute the visibility of spatial depth in his Essay Towards a New Theory of Vision. Kant referred to the experience of space in his Critique of Pure Reason as being a pure a priori form of intuition. In the 19th and 20th centuries mathematicians began to examine geometries that are non-Euclidean, in space is conceived as curved. According to Albert Einsteins theory of relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have confirmed that non-Euclidean geometries provide a model for the shape of space. In the seventeenth century, the philosophy of space and time emerged as an issue in epistemology. At its heart, Gottfried Leibniz, the German philosopher-mathematician, and Isaac Newton, unoccupied regions are those that could have objects in them, and thus spatial relations with other places. For Leibniz, then, space was an abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete. Space could be thought of in a way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people, but since there would be no observational way of telling these universes apart then, according to the identity of indiscernibles, there would be no real difference between them. According to the principle of sufficient reason, any theory of space that implied that there could be two possible universes must therefore be wrong. Newton took space to be more than relations between objects and based his position on observation and experimentation
30.
Force
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In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity, force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity and it is measured in the SI unit of newtons and represented by the symbol F. The original form of Newtons second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. In an extended body, each part usually applies forces on the adjacent parts, such internal mechanical stresses cause no accelation of that body as the forces balance one another. Pressure, the distribution of small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of materials, or flow in fluids. In part this was due to an understanding of the sometimes non-obvious force of friction. A fundamental error was the belief that a force is required to maintain motion, most of the previous misunderstandings about motion and force were eventually corrected by Galileo Galilei and Sir Isaac Newton. With his mathematical insight, Sir Isaac Newton formulated laws of motion that were not improved-on for nearly three hundred years, the Standard Model predicts that exchanged particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known, in order of decreasing strength, they are, strong, electromagnetic, weak, high-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction. Since antiquity the concept of force has been recognized as integral to the functioning of each of the simple machines. The mechanical advantage given by a machine allowed for less force to be used in exchange for that force acting over a greater distance for the same amount of work. Analysis of the characteristics of forces ultimately culminated in the work of Archimedes who was famous for formulating a treatment of buoyant forces inherent in fluids. Aristotle provided a discussion of the concept of a force as an integral part of Aristotelian cosmology. In Aristotles view, the sphere contained four elements that come to rest at different natural places therein. Aristotle believed that objects on Earth, those composed mostly of the elements earth and water, to be in their natural place on the ground. He distinguished between the tendency of objects to find their natural place, which led to natural motion, and unnatural or forced motion
31.
Baseball (ball)
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A baseball is a ball used in the sport of the same name, baseball. The ball features a rubber or cork center, wrapped in yarn and it is 9. 00–9.25 inches in circumference, and masses from 5.00 to 5.25 ounces. The yarn or string used to wrap the baseball can be up to one mile in length, some are wrapped in a plastic-like covering. A significant characteristic of the baseball is the stitching that holds together the covering of the ball, after a ball has been pitched, these raised stitches act like wings on a plane, catching the wind and causing the ball to swerve slightly on its way to the catcher. See, for example, curveball, slider, two-seam fastball, four-seam fastball, in the early, mid-1800s days of baseball, there was a great variety in the size, shape, weight, and manufacturing of baseballs. Early baseballs were made from a core from old, melted shoes, wrapped in yarn. Fish eyes were used as cores in some places. Pitchers usually made their own balls, which were used throughout the game, one of the more popular earlier ball designs was the lemon peel ball, named after its distinct four lines of stitching design. Lemon peel balls were darker, smaller, and weighed less than other baseballs, prompting them to further and bounce higher. In the mid-1850s, teams in New York met in attempt to standardize the baseball and they decided to regulate baseballs to weighing between 5. 5-6 oz and having a circumference of 8-11 inches. There were still many variations of baseballs since they were completely handmade, balls with more rubber and a tighter winding went further and faster, and balls with less rubber and a looser winding did not travel as far or fast. This is generally true for all baseballs, teams often used this knowledge to their advantage, as players from the team usually manufactured their own baseballs to use in games. There is no agreement on who invented the commonplace figure-8 stitching on baseballs, some historians say that it was invented by Ellis Drake, a shoemakers son, to make the cover stronger and more durable. Others say it was invented by Colonel William A. Cutler, Harwood built a factory in Natick, Massachusetts, and was the first to popularize and mass-produce baseballs with the figure-8 design. In 1876, the National League was created, and standard rules, a. G. Spalding, a well-known baseball pitcher who made his own balls, convinced the NL to adopt his ball as the official baseball for the NL. It remained that way for 100 years, in 1910, the cork-core ball was introduced. They outlasted rubber core baseballs, and for the first few years they were used and it eventually went back to normal. Pitchers adapted with the use of the spitball, which is now illegal, in 1920, a couple of important changes were made to baseballs
32.
Ranged weapon
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A ranged weapon is any weapon that can harm targets at distances greater than hand-to-hand distance. In contrast, a weapon intended to be used in combat is called a melee weapon. Ranged weapons give the attacker an advantage in combat since the target has less time to react and it also provides a safer combat option since melee combat often becomes a life or death struggle where each member has a high probability of dying. The line between ranged and melee weapons is not entirely definite, for instance, spears, knives, early ranged weapons include thrown weapons such as javelins, slings, darts, the bow and arrow, and medieval siege engines like stone throwers, catapults, ballistas and trebuchets. Siege engines were used for passing or hitting obstacles like fortifications. After the invention of gunpowder and the development of firearms, ranged weapons became the weapon of choice, in modern warfare, ranged weaponry is used in the form of cruise and ballistic missiles. Maximum effective range of a weapon is the greatest distance fired, while some are small and light enough to be used by individuals, most require a team to aim, move or fire. ISBN 1-58574-478-6 The Traditional Bowyers Bible Volume 1, the Traditional Bowyers Bible Volume 2. The Traditional Bowyers Bible Volume 3, the ballistics of the sling, Thom Richardson, Royal Armouries Yearbook, Volume 31998
33.
Equations of motion
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In mathematical physics, equations of motion are equations that describe the behaviour of a physical system in terms of its motion as a function of time. The most general choice are generalized coordinates which can be any convenient variables characteristic of the physical system, the functions are defined in a Euclidean space in classical mechanics, but are replaced by curved spaces in relativity. If the dynamics of a system is known, the equations are the solutions to the equations describing the motion of the dynamics. There are two descriptions of motion, dynamics and kinematics. Dynamics is general, since momenta, forces and energy of the particles are taken into account, in this instance, sometimes the term refers to the differential equations that the system satisfies, and sometimes to the solutions to those equations. However, kinematics is simpler as it concerns only variables derived from the positions of objects, equations of motion can therefore be grouped under these main classifiers of motion. In all cases, the types of motion are translations, rotations, oscillations. A differential equation of motion, usually identified as some physical law, solving the differential equation will lead to a general solution with arbitrary constants, the arbitrariness corresponding to a family of solutions. A particular solution can be obtained by setting the initial values, to state this formally, in general an equation of motion M is a function of the position r of the object, its velocity, and its acceleration, and time t. Euclidean vectors in 3D are denoted throughout in bold and this is equivalent to saying an equation of motion in r is a second order ordinary differential equation in r, M =0, where t is time, and each overdot denotes one time derivative. The initial conditions are given by the constant values at t =0, r, r ˙, the solution r to the equation of motion, with specified initial values, describes the system for all times t after t =0. Sometimes, the equation will be linear and is likely to be exactly solvable. In general, the equation will be non-linear, and cannot be solved exactly so a variety of approximations must be used, the solutions to nonlinear equations may show chaotic behavior depending on how sensitive the system is to the initial conditions. Despite the great strides made in the development of geometry made by Ancient Greeks and surveys in Rome, the exposure of Europe to Arabic numerals and their ease in computations encouraged first the scholars to learn them and then the merchants and invigorated the spread of knowledge throughout Europe. These studies led to a new body of knowledge that is now known as physics, thomas Bradwardine, one of those scholars, extended Aristotelian quantities such as distance and velocity, and assigned intensity and extension to them. Bradwardine suggested a law involving force, resistance, distance, velocity. Nicholas Oresme further extended Bradwardines arguments, for writers on kinematics before Galileo, since small time intervals could not be measured, the affinity between time and motion was obscure. They used time as a function of distance, and in free fall, de Sotos comments are shockingly correct regarding the definitions of acceleration and the observation that during the violent motion of ascent acceleration would be negative
34.
Ball
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A ball is a round object with various uses. It is used in games, where the play of the game follows the state of the ball as it is hit. Balls can also be used for activities, such as catch, marbles. Balls made from hard-wearing materials are used in engineering applications to very low friction bearings. Black-powder weapons use stone and metal balls as projectiles, although many types of balls are today made from rubber, this form was unknown outside the Americas until after the voyages of Columbus. The Spanish were the first Europeans to see bouncing rubber balls which were employed most notably in the Mesoamerican ballgame, balls used in various sports in other parts of the world prior to Columbus were made from other materials such as animal bladders or skins, stuffed with various materials. As balls are one of the most familiar spherical objects to humans, no Old English representative of any of these is known. If ball- was native in Germanic, it may have been a cognate with the Latin foll-is in sense of a blown up or inflated. In the later Middle English spelling balle the word coincided graphically with the French balle ball, French balle is assumed to be of Germanic origin, itself, however. In Ancient Greek the word πάλλα for ball is attested besides the word σφαίρα, a ball, as the essential feature in many forms of gameplay requiring physical exertion, must date from the very earliest times. A rolling object appeals not only to a baby but to a kitten. Some form of game with a ball is found portrayed on Egyptian monuments, in Homer, Nausicaa was playing at ball with her maidens when Odysseus first saw her in the land of the Phaeacians. And Halios and Laodamas performed before Alcinous and Odysseus with ball play, of regular rules for the playing of ball games, little trace remains, if there were any such. Pollux mentions a game called episkyros, which has often been looked on as the origin of football and it seems to have been played by two sides, arranged in lines, how far there was any form of goal seems uncertain. Among the Romans, ball games were looked upon as an adjunct to the bath, and were graduated to the age and health of the bathers and this was struck from player to player, who wore a kind of gauntlet on the arm. These games are known to us through the Romans, though the names are Greek, the various modern games played with a ball or balls and subject to rules are treated under their various names, such as polo, cricket, football, etc. Several sports use a ball in the shape of a prolate spheroid, Ball Buckminster Fullerene Football Kickball Marbles Penny floater Prisoner Ball Shuttlecock Super Ball
35.
Arrow
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An arrow is a shafted projectile that is shot with a bow. It predates recorded history and is common to most cultures, an arrow usually consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other. The oldest evidence of stone-tipped projectiles, which may or may not have been propelled by a bow, dating to c.64,000 years ago, were found in Sibudu Cave, South Africa. The oldest evidence of the use of bows to shoot arrows dates to about 10,000 years ago and they had shallow grooves on the base, indicating that they were shot from a bow. The oldest bow so far recovered is about 8,000 years old, archery seems to have arrived in the Americas with the Arctic small tool tradition, about 4,500 years ago. Arrow sizes vary greatly across cultures, ranging from eighteen inches to five feet, however, most modern arrows are 75 centimetres to 96 centimetres, most war arrows from an English ship sunk in 1545 were 76 centimetres. Very short arrows have been used, shot through a guide attached either to the bow or to the archers wrist and these may fly farther than heavier arrows, and an enemy without suitable equipment may find himself unable to return them. The shaft is the structural element of the arrow, to which the other components are attached. Traditional arrow shafts are made from wood, bamboo or reeds, while modern shafts may be made from aluminium, carbon fibre reinforced plastic. Such shafts are made from an aluminium core wrapped with a carbon fibre outer. The stiffness of the shaft is known as its spine, referring to how little the shaft bends when compressed, hence, an arrow which bends less is said to have more spine. In order to strike consistently, a group of arrows must be similarly spined, center-shot bows, in which the arrow passes through the central vertical axis of the bow riser, may obtain consistent results from arrows with a wide range of spines. Higher draw-weight bows will generally require stiffer arrows, with more spine to give the amount of flex when shot. The weight of a shaft can be expressed in GPI. The length of a shaft in inches multiplied by its GPI rating gives the weight of the shaft in grains, for example, a shaft that is 30 inches long and has a GPI of 9.5 weighs 285 grains, or about 18 grams. This does not include the elements of a finished arrow. Sometimes a shaft will be made of two different types of wood fastened together, resulting in what is known as a footed arrow, known by some as the finest of wood arrows, footed arrows were used both by early Europeans and Native Americans. Footed arrows will typically consist of a length of hardwood near the head of the arrow
36.
Shell (projectile)
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A shell is a payload-carrying projectile that, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used, originally, it was called a bombshell, but shell has come to be unambiguous in a military context. Words cognate with grenade are still used for an artillery or mortar projectile in some European languages, shells are usually large-calibre projectiles fired by artillery, combat vehicles, and warships. Shells usually have the shape of a cylinder topped by a nose for good aerodynamic performance, possibly with a tapering base. Solid cannonballs did not need a fuse, but hollow munitions filled with something such as gunpowder to fragment the ball, needed a fuse, percussion fuses with a spherical projectile presented a challenge because there was no way of ensuring that the impact mechanism hit the target. Therefore, shells needed a fuse that was ignited before or during firing. The earliest record of shells being used in combat was by the Republic of Venice at Jadra in 1376, shells with fuses were used at the 1421 siege of St Boniface in Corsica. These were two hollowed hemispheres of stone or bronze held together by an iron hoop, as described in their book, these hollow, gunpowder-packed shells were made of cast iron. At least since the 16th Century grenades made of ceramics or glass were in use in Central Europe, a hoard of several hundred ceramic greandes were discovered during building works in front of a bastion of the Bavarian City of Ingolstadt, Germany dated to the 17th Century. Lots of the grenades obtained their orignal blackpowder loads and igniters, most probably the grenades were intentionally dumped the moat of the bastion before the year 1723. Early powder burning fuses had to be loaded fuse down to be ignited by firing or a portfire put down the barrel to light the fuse, other shells were wrapped in bitumen cloth, which would ignite during the firing and in turn ignite a powder fuse. Nevertheless, shells came into use in the 16th Century. By the 18th Century, it was known that the fuse towards the muzzle could be lit by the flash through the windage between the shell and the barrel, the use of exploding shells from field artillery became relatively commonplace from early in the 19th century. Until the mid 19th century, shells remained as simple exploding spheres that used gunpowder and they were usually made of cast iron, but bronze, lead, brass and even glass shell casings were experimented with. The word bomb encompassed them at the time, as heard in the lyrics of The Star-Spangled Banner, typically, the thickness of the metal body was about a sixth of their diameter and they were about two thirds the weight of solid shot of the same calibre. To ensure that shells were loaded with their fuses towards the muzzle, in 1819, a committee of British artillery officers recognised that they were essential stores and in 1830 Britain standardised sabot thickness as a half inch. The sabot was also intended to reduce jamming during loading, despite the use of exploding shell, the use of smoothbore cannons, firing spherical projectiles of shot, remained the dominant artillery method until the 1850s. By the late 18th century, artillery could use canister shot to defend itself from infantry or cavalry attack and this involved loading a tin or canvas container filled with small iron or lead balls instead of the usual cannonball
37.
Throwing
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Throwing is the launching of a ballistic projectile by hand. This action is possible for animals with the ability to grasp objects with their hands. Humans, being bipedal, have a variety of throwing techniques and abilities. These have been employed in warfare – first through rock-throwing, then refined weapon-throwing, Throwing is used in many sports and games, particularly ball games, and in throwing sports the action is the main determiner of the outcome. These serve as forms of recreation and exercise in society, humans are believed to be unusually good throwers due to their high dexterity and good timing capabilities, and it is believed that this is an evolved trait. Evidence of hominid throwing dates back 2 million years to homo erectus, the 90 mph throwing speed found in many athletes far exceeds the speed at which chimpanzees can throw things, which is about 20 mph. This ability reflects the ability of the shoulder muscles and tendons to store elasticity until it is needed to propel an object. Types of throws include overhand throws, underhand throws and using both hands, overhand throws are thrown predominantly above the shoulder, underhand throws below. Overhand throws are usually faster, and ball speeds of 105 miles per hour have been recorded in baseball. Thrown objects are often spun for stability or aerodynamic effects. It is used almost exclusively in athletic events, the throwing motion can be broken down into three basic steps, cocking, accelerating, and releasing. Desired qualities in the produce a fast, accurate throw. These qualities are affected by the attributes of the thrower like height, strength. However it is mainly the throwing motion mechanics and the ability to coordinate them that determines the quality of the throw. Determining the desired qualities of the motion is difficult to assess due to the extremely short amount of time that it takes professionals to perform the motion. Throwing is used for propelling weapons such as stones or spears at enemies, predators, shurikenjutsu are traditional Japanese thrown weapons Hand grenades are thrown explosives Pitching or bowling in bat-and-ball games, e. g. The weight throw is the fifth most common field throwing event, males are often found to be better at throwing. However, it unclear whether this is biologically or culturally based
38.
Baseball
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Baseball is a bat-and-ball game played between two teams of nine players each, who take turns batting and fielding. A run is scored when a player advances around the bases, Players on the batting team take turns hitting against the pitcher of the fielding team, which tries to prevent runs by getting hitters out in any of several ways. A player on the team who reaches a base safely can later attempt to advance to subsequent bases during teammates turns batting. The teams switch between batting and fielding whenever the team records three outs. One turn batting for both teams, beginning with the team, constitutes an inning. A game is composed of nine innings, and the team with the number of runs at the end of the game wins. Baseball has no clock, although almost all games end in the ninth inning. Baseball evolved from older bat-and-ball games already being played in England by the mid-18th century and this game was brought by immigrants to North America, where the modern version developed. By the late 19th century, baseball was widely recognized as the sport of the United States. Baseball is now popular in North America and parts of Central and South America, the Caribbean, in the United States and Canada, professional Major League Baseball teams are divided into the National League and American League, each with three divisions, East, West, and Central. The major league champion is determined by playoffs that culminate in the World Series, the top level of play is similarly split in Japan between the Central and Pacific Leagues and in Cuba between the West League and East League. The evolution of baseball from older bat-and-ball games is difficult to trace with precision, a French manuscript from 1344 contains an illustration of clerics playing a game, possibly la soule, with similarities to baseball. Other old French games such as thèque, la balle au bâton, consensus once held that todays baseball is a North American development from the older game rounders, popular in Great Britain and Ireland. Baseball Before We Knew It, A Search for the Roots of the Game, by David Block, suggests that the game originated in England, recently uncovered historical evidence supports this position. Block argues that rounders and early baseball were actually regional variants of other. It has long believed that cricket also descended from such games. The earliest known reference to baseball is in a 1744 British publication, A Little Pretty Pocket-Book, David Block discovered that the first recorded game of Bass-Ball took place in 1749 in Surrey, and featured the Prince of Wales as a player. William Bray, an English lawyer, recorded a game of baseball on Easter Monday 1755 in Guildford and this early form of the game was apparently brought to Canada by English immigrants
39.
Chimpanzee
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Chimpanzees are one of the two species of the genus Pan, the other being the bonobo. Together with gorillas, they are the only exclusively African species of ape that are currently extant. Native to sub-Saharan Africa, both chimpanzees and bonobos are found in the Congo jungle. In addition, P. troglodytes is divided into four subspecies, based on genome sequencing, the two extant Pan species diverged around one million years ago. The most obvious differences are that chimpanzees are somewhat larger, more aggressive and male-dominated, while the bonobos are more gracile, peaceful and their hair is typically black or brown. Males and females differ in size and appearance, both chimps and bonobos are some of the most social great apes, with social bonds occurring among individuals in large communities. Fruit is the most important component of a diet, however, they will also eat vegetation, bark, honey, insects. They can live over 30 years in both the wild and captivity, Chimpanzees and bonobos are equally humanitys closest living relatives. As such, they are among the largest-brained, and most intelligent of primates, they use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and they have both been extensively studied for their learning abilities. There may even be distinctive cultures within populations, field studies of Pan troglodytes were pioneered by primatologist Jane Goodall. Both Pan species are considered to be endangered as human activities have caused declines in the populations. Threats to wild populations include poaching, habitat destruction. Several conservation and rehabilitation organisations are dedicated to the survival of Pan species in the wild, the first use of the name chimpanze is recorded in The London Magazine in 1738, glossed as meaning mockman in a language of the Angolans. The spelling chimpanzee is found in a 1758 supplement to Chambers Cyclopædia, the colloquialism chimp was most likely coined some time in the late 1870s. The common chimpanzee was named Simia troglodytes by Johann Friedrich Blumenbach in 1776, the species name troglodytes is a reference to the Troglodytae, an African people described by Greco-Roman geographers. Blumenbach first used it in his De generis humani varietate nativa liber in 1776, the genus name Pan was first introduced by Lorenz Oken in 1816. An alternative Theranthropus was suggested by Brookes 1828 and Chimpansee by Voigt 1831, troglodytes was not available, as it had been given as the name of a genus of wren in 1809. The International Commission on Zoological Nomenclature adopted Pan as the official name of the genus in 1895
40.
Tendon
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A tendon or sinew is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments, both are made of collagen, ligaments join one bone to another bone, while tendons connect muscle to bone. Histologically, tendons consist of dense connective tissue fascicles encased in dense irregular connective tissue sheaths. Normal healthy tendons are composed mostly of parallel arrays of collagen fibers closely packed together, the collagen portion is made up of 97–98% type I collagen, with small amounts of other types of collagen. After secretion from the cell, the peptides are cleaved by procollagen N- and C-proteinases. A collagen molecule is about 300 nm long and 1–2 nm wide, and the diameter of the fibrils that are formed can range from 50–500 nm. In tendons, the fibrils then assemble further to form fascicles, which are about 10 mm in length with a diameter of 50–300 μm, fascicles are bound by the endotendineum, which is a delicate loose connective tissue containing thin collagen fibrils. and elastic fibres. Groups of fascicles are bounded by the epitenon, filling the interstitia within the fascia where the tendon is located is the paratenon a fatty areolar tissue. The major GAG components of the tendon are dermatan sulfate and chondroitin sulfate, the dermatan sulfate side chains of decorin aggregate in solution, and this behavior can assist with the assembly of the collagen fibrils. The tenocytes produce the collagen molecules, which aggregate end-to-end and side-to-side to produce collagen fibrils, fibril bundles are organized to form fibres with the elongated tenocytes closely packed between them. There is a network of cell processes associated with collagen in the tendon. The cells communicate with other through gap junctions, and this signalling gives them the ability to detect. Blood vessels may be visualized within the endotendon running parallel to collagen fibres, the internal tendon bulk is thought to contain no nerve fibres, but the epitenon and paratenon contain nerve endings, while Golgi tendon organs are present at the junction between tendon and muscle. Tendon length varies in all groups and from person to person. Tendon length is, in practice, the deciding factor regarding actual and potential muscle size, successful bodybuilders will generally have shorter tendons. Conversely, in sports requiring athletes to excel in such as running or jumping, it is beneficial to have longer than average Achilles tendon. Traditionally, tendons have been considered to be a mechanism by which muscles connect to bone and this connection allows tendons to passively modulate forces during locomotion, providing additional stability with no active work. However, over the past two decades, much research focused on the properties of some tendons and their ability to function as springs
41.
Elasticity (physics)
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In physics, elasticity is the ability of a body to resist a distorting influence or deforming force and to return to its original size and shape when that influence or force is removed. Solid objects will deform when adequate forces are applied on them, if the material is elastic, the object will return to its initial shape and size when these forces are removed. The physical reasons for elastic behavior can be different for different materials. In metals, the atomic lattice changes size and shape when forces are applied, when forces are removed, the lattice goes back to the original lower energy state. For rubbers and other polymers, elasticity is caused by the stretching of polymer chains when forces are applied, perfect elasticity is an approximation of the real world. The most elastic body in modern science found is Quartz fibre which is not even a perfect elastic body, so perfect elastic body is an ideal concept only. Most materials which possess elasticity in practice remain purely elastic only up to very small deformations. In engineering, the amount of elasticity of a material is determined by two types of material parameter, the first type of material parameter is called a modulus, which measures the amount of force per unit area needed to achieve a given amount of deformation. The SI unit of modulus is the pascal, a higher modulus typically indicates that the material is harder to deform. The second type of measures the elastic limit, the maximum stress that can arise in a material before the onset of permanent deformation. Its SI unit is also pascal, when describing the relative elasticities of two materials, both the modulus and the elastic limit have to be considered. Rubbers typically have a low modulus and tend to stretch a lot, of two rubber materials with the same elastic limit, the one with a lower modulus will appear to be more elastic, which is however not correct. When an elastic material is deformed due to a force, it experiences internal resistance to the deformation. The various moduli apply to different kinds of deformation, for instance, Youngs modulus applies to extension/compression of a body, whereas the shear modulus applies to its shear. The elasticity of materials is described by a curve, which shows the relation between stress and strain. The curve is nonlinear, but it can be approximated as linear for sufficiently small deformations. For even higher stresses, materials exhibit behavior, that is, they deform irreversibly. Elasticity is not exhibited only by solids, non-Newtonian fluids, such as viscoelastic fluids, in response to a small, rapidly applied and removed strain, these fluids may deform and then return to their original shape. Under larger strains, or strains applied for longer periods of time, because the elasticity of a material is described in terms of a stress-strain relation, it is essential that the terms stress and strain be defined without ambiguity
42.
Sling (weapon)
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A sling is a projectile weapon typically used to throw a blunt projectile such as a stone, clay, or lead sling-bullet. It is also known as the shepherds sling, someone who specialises in using slings is called a slinger. A sling has a cradle or pouch in the middle of two lengths of cord. The sling stone is placed in the pouch, the middle finger or thumb is placed through a loop on the end of one cord, and a tab at the end of the other cord is placed between the thumb and forefinger. The sling is swung in an arc, and the tab released at a precise moment and this frees the projectile to fly to the target. The sling essentially works by extending the length of a human arm, the sling is inexpensive and easy to build. It has historically used for hunting game and in combat. Film exists of Spanish Civil War combatants using slings to throw grenades over buildings into enemy positions on the opposite street, today the sling is of interest as a wilderness survival tool and an improvised weapon. The sling is an ancient weapon known to Neolithic peoples around the Mediterranean and it is possible that the sling was invented during the Upper Paleolithic at a time when new technologies such as the spear-thrower and the bow and arrow were emerging. Whereas sling-bullets are common finds in the record, slings themselves are rare. This is both because a slings materials are biodegradable and because slings were lower-status weapons, rarely preserved in a wealthy person’s grave, the oldest-known surviving slings—radiocarbon dated to ca.2500 BC—were recovered from South American archaeological sites located on the coast of Peru. The oldest-known surviving North American sling—radiocarbon dated to ca.1200 BC—was recovered from Lovelock Cave, the oldest known extant slings from the Old World were found in the tomb of Tutankhamen, who died about 1325 BC. A pair of finely plaited slings were found with other weapons, the sling was probably intended for the departed pharaoh to use for hunting game. It was found alongside an iron spearhead, the remains are broken into three sections. The oldest representation of a slinger in art may be from Çatalhöyük, from approximately 7,000 BC, the sling is mentioned by Homer and by other Greek authors. This deficiency was rectified when a company of 200 Rhodians, who understood the use of leaden sling-bullets, was formed and they were able, says Xenophon, to project their missiles twice as far as the Persian slingers, who used large stones. Ancient authors seemed to believe, incorrectly, that sling-bullets could penetrate armour, in the first instance, it seems likely that the authors were indicating that slings could cause injury through armour by a percussive effect rather than by penetration. In the latter case we may imagine that they were impressed by the degree of deformation suffered by lead sling-bullet after hitting a hard target, various ancient peoples enjoyed a reputation for skill with the sling
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