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Throws
Throwing is an action which consists in accelerating a projectile and then releasing it so that it follows a ballistic trajectory, usually with the aim of impacting a remote target. This action is best characterized for animals with prehensile limbs: in this case the projectile is grasped, while the limb segments impart a motion of the hand through compounded mechanical advantage. For other animals, the definition of throwing is somewhat unclear, as other actions such as spitting or spraying may or may not be included. Primates are the most capable throwers in the animal kingdom, and they typically throw feces as a form of agonistic behavior. Of all primates, humans are by far the most capable throwers. They throw a large variety of projectiles, with a much greater efficacy and accuracy. Humans have thrown projectiles for hunting and in warfare – first through rock-throwing, then refined weapon-throwing (e.g. spear), and into modern day with hand grenades and tear gas cani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Throwing Rocks (3843366278)
Throwing is an action which consists in accelerating a projectile and then releasing it so that it follows a ballistic trajectory, usually with the aim of impacting a remote target. This action is best characterized for animals with prehensile limbs: in this case the projectile is grasped, while the limb segments impart a motion of the hand through compounded mechanical advantage. For other animals, the definition of throwing is somewhat unclear, as other actions such as spitting or spraying may or may not be included. Primates are the most capable throwers in the animal kingdom, and they typically throw feces as a form of agonistic behavior. Of all primates, humans are by far the most capable throwers. They throw a large variety of projectiles, with a much greater efficacy and accuracy. Humans have thrown projectiles for hunting and in warfare – first through rock-throwing, then refined weapon-throwing (e.g. spear), and into modern day with hand grenades and tear gas cani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hand Grenade
A grenade is an explosive weapon typically thrown by hand (also called hand grenade), but can also refer to a shell (explosive projectile) shot from the muzzle of a rifle (as a rifle grenade) or a grenade launcher. A modern hand grenade generally consists of an explosive charge ("filler"), a detonator mechanism, an internal striker to trigger the detonator, and a safety lever secured by a cotter pin. The user removes the safety pin before throwing, and once the grenade leaves the hand the safety lever gets released, allowing the striker to trigger a primer that ignites a fuze (sometimes called the delay element), which burns down to the detonator and explodes the main charge. Grenades work by dispersing fragments (fragmentation grenades), shockwaves (high-explosive, anti-tank and stun grenades), chemical aerosols (smoke and gas grenades) or fire ( incendiary grenades). Fragmentation grenades ("frags") are probably the most common in modern armies, and when the word ''gre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ballistics
Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially ranged weapon munitions such as bullets, unguided bombs, rockets or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance. A ballistic body is a free-moving body with momentum which can be subject to forces such as the forces exerted by pressurized gases from a gun barrel or a propelling nozzle, normal force by rifling, and gravity and air drag during flight. A ballistic missile is a missile that is guided only during the relatively brief initial phase of powered flight and the trajectory is subsequently governed by the laws of classical mechanics; in contrast to (for example) a cruise missile which is aerodynamically guided in powered flight like a fixed-wing aircraft. History and prehistory The earliest known ballistic projectiles were stones and spears, and the throwing stick. The oldes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ranged Weapons
A ranged weapon is any weapon that can engage targets beyond hand-to-hand distance, i.e. at distances greater than the physical reach of the user holding the weapon itself. The act of using such a weapon is also known as shooting. It is sometimes also called projectile weapon or missile weapon because it typically works by launching solid projectiles ("missiles"), though technically a fluid-projector (which throws out pressurized streams of liquid or even gas) and a directed-energy weapon (which does not involve any tangible projectile) are also ranged weapons. In contrast, a weapon intended to be used in hand-to-hand combat is called a melee weapon. Ranged weapons give the attacker an advantage, since the target is often getting hit from beyond immediate visual range, therefore making it more difficult for the defenders to react and hitting back effectively. It also puts distance between the attacker and the opponent, which is a safer combat option since the close physical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Games
A game is a structured form of play, usually undertaken for entertainment or fun, and sometimes used as an educational tool. Many games are also considered to be work (such as professional players of spectator sports or games) or art (such as jigsaw puzzles or games involving an artistic layout such as Mahjong, solitaire, or some video games). Games are sometimes played purely for enjoyment, sometimes for achievement or reward as well. They can be played alone, in teams, or online; by amateurs or by professionals. The players may have an audience of non-players, such as when people are entertained by watching a chess championship. On the other hand, players in a game may constitute their own audience as they take their turn to play. Often, part of the entertainment for children playing a game is deciding who is part of their audience and who is a player. A toy and a game are not the same. Toys generally allow for unrestricted play whereas games come with present rules. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sports
Sport pertains to any form of competitive physical activity or game that aims to use, maintain, or improve physical ability and skills while providing enjoyment to participants and, in some cases, entertainment to spectators. Sports can, through casual or organized participation, improve participants' physical health. Hundreds of sports exist, from those between single contestants, through to those with hundreds of simultaneous participants, either in teams or competing as individuals. In certain sports such as racing, many contestants may compete, simultaneously or consecutively, with one winner; in others, the contest (a ''match'') is between two sides, each attempting to exceed the other. Some sports allow a "tie" or "draw", in which there is no single winner; others provide tie-breaking methods to ensure one winner and one loser. A number of contests may be arranged in a tournament producing a champion. Many sports leagues make an annual champion by arranging games in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exercise
Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic skills, weight loss or maintenance, improve health, or simply for enjoyment. Many individuals choose to exercise outdoors where they can congregate in groups, socialize, and improve well-being as well as mental health. In terms of health benefits, the amount of recommended exercise depends upon the goal, the type of exercise, and the age of the person. Even doing a small amount of exercise is healthier than doing none. Classification Physical exercises are generally grouped into three types, depending on the overall effect they have on the human body: * Aerobic exercise is any physical activity that uses large muscle groups and causes the body to use more oxygen than it would while resting. The goal of aerobic exercise is to increa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recreation
Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or pleasure and are considered to be "fun". Etymology The term ''recreation'' appears to have been used in English first in the late 14th century, first in the sense of "refreshment or curing of a sick person", and derived turn from Latin (''re'': "again", ''creare'': "to create, bring forth, beget"). Prerequisites to leisure People spend their time on activities of daily living, work, sleep, social duties and leisure, the latter time being free from prior commitments to physiologic or social needs, a prerequisite of recreation. Leisure has increased with increased longevity and, for many, with decreased hours spent for physical and economic survival, yet others argue that time pressure has increased for modern people, as they are committed to too ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gun Powder
Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). The sulfur and carbon act as fuels while the saltpeter is an oxidizer. Gunpowder has been widely used as a propellant in firearms, artillery, rocketry, and pyrotechnics, including use as a blasting agent for explosives in quarrying, mining, building pipelines and road building. Gunpowder is classified as a low explosive because of its relatively slow decomposition rate and consequently low brisance. Low explosives deflagrate (i.e., burn at subsonic speeds), whereas high explosives detonate, producing a supersonic shockwave. Ignition of gunpowder packed behind a projectile generates enough pressure to force the shot from the muzzle at high speed, but usually not enough force to rupture the gun barrel. It thus makes a good propellan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanism (engineering)
In engineering, a mechanism is a Machine, device that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components which may include: * Gears and gear trains; * belt drive, Belts and chain drives; * Cams and cam follower, followers; * Linkage (mechanical), Linkages; * Friction devices, such as brakes or clutches; * Structural components such as a frame, fasteners, bearings, springs, or lubricants; * Various machine elements, such as splines, pins, or keys. The German scientist Franz Reuleaux defines ''machine'' as "a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion". In this context, his use of ''machine'' is generally interpreted to mean ''mechanism''. The combination of force and movement defines Power (physics), power, and a mechanism manages power to achieve a desired set of forces and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catapult
A catapult is a ballistic device used to launch a projectile a great distance without the aid of gunpowder or other propellants – particularly various types of ancient and medieval siege engines. A catapult uses the sudden release of stored potential energy to propel its payload. Most convert tension or torsion energy that was more slowly and manually built up within the device before release, via springs, bows, twisted rope, elastic, or any of numerous other materials and mechanisms. In use since ancient times, the catapult has proven to be one of the most persistently effective mechanisms in warfare. In modern times the term can apply to devices ranging from a simple hand-held implement (also called a "slingshot") to a mechanism for launching aircraft from a ship. The earliest catapults date to at least the 7th century BC, with King Uzziah, of Judah, recorded as equipping the walls of Jerusalem with machines that shot "great stones". Catapults are mentioned in Yajurveda un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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