Misplaced Pages

#521478

49-516: Other names include catapult (United Kingdom), peashooter (United States), gulel (India), kettie (South Africa), or ging , shanghai , pachoonga (Australia and New Zealand) Slingshots depend on strong elastic materials for their projectile firepower, typically vulcanized natural rubber or the equivalent such as silicone rubber tubing, and thus date no earlier than the invention of vulcanized rubber by Charles Goodyear in 1839 (patented in 1844). By 1860, this "new engine" had established

98-449: A 1946 Popular Science article details a slingshot builder and hunter using home-built slingshots made from forked dogwood sticks to take small game at ranges of up to 9 m (30 ft) with No. 0 lead buckshot (8 mm [0.32 in] diameter). The Wham-O company, founded in 1948, produced the Wham-O slingshot. It was made of ash wood and used flat rubber bands. The Wham-O

147-468: A 90-degree rotation; both these deformations have the same spatial strain tensors yet must produce different values of the Cauchy stress tensor. Even though the stress in a Cauchy-elastic material depends only on the state of deformation, the work done by stresses might depend on the path of deformation. Therefore, Cauchy elasticity includes non-conservative "non-hyperelastic" models (in which work of deformation

196-558: A degree that many subsequent paramilitary organisations have been known by that title – most notably the Provisional Irish Republican Army , which was a key participant during the Troubles in the north of Ireland. The contemporary IRA organisations each claim the sole right to the name, each insisting they are the original IRA's only legitimate descendant. The playwright and former IRA member Brendan Behan once said that

245-501: A function of the deformation gradient ( F {\displaystyle {\boldsymbol {F}}} ). By also requiring satisfaction of material objectivity , the energy potential may be alternatively regarded as a function of the Cauchy-Green deformation tensor ( C := F T F {\displaystyle {\boldsymbol {C}}:={\boldsymbol {F}}^{\textsf {T}}{\boldsymbol {F}}} ), in which case

294-468: A given isotropic solid , with known theoretical elasticity for the bulk material in terms of Young's modulus,the effective elasticity will be governed by porosity . Generally a more porous material will exhibit lower stiffness. More specifically, the fraction of pores, their distribution at different sizes and the nature of the fluid with which they are filled give rise to different elastic behaviours in solids. For isotropic materials containing cracks,

343-411: A one-dimensional rod, can often be reduced to applications of Hooke's law. The elastic behavior of objects that undergo finite deformations has been described using a number of models, such as Cauchy elastic material models, Hypoelastic material models, and Hyperelastic material models. The deformation gradient ( F ) is the primary deformation measure used in finite strain theory . A material

392-415: A part-time manufacturer of the aluminium -framed John Milligan Special, a hunting slingshot, reported that about a third of his customers were physicians. Slingshots are also occasionally used in angling to disperse bait over an area of water, so that fish may be attracted. A home-made derivative of a slingshot also exists, consisting of a rubber balloon cut in half and tied to a tubular object such as

441-479: A reputation for use by juveniles in vandalism. For much of their early history, slingshots were a "do-it-yourself" item, typically made from a forked branch to form the Y-shaped handle, with rubber strips sliced from items such as inner tubes or other sources of good vulcanized rubber, and using suitably sized stones. While early slingshots were most associated with young vandals, they could be effective hunting arms in

490-455: A special case, which prompts some constitutive modelers to append a third criterion that specifically requires a hypoelastic model to not be hyperelastic (i.e., hypoelasticity implies that stress is not derivable from an energy potential). If this third criterion is adopted, it follows that a hypoelastic material might admit nonconservative adiabatic loading paths that start and end with the same deformation gradient but do not start and end at

539-527: Is a constant known as the rate or spring constant . It can also be stated as a relationship between stress σ {\displaystyle \sigma } and strain ε {\displaystyle \varepsilon } : where E is known as the Young's modulus . Although the general proportionality constant between stress and strain in three dimensions is a 4th-order tensor called stiffness , systems that exhibit symmetry , such as

SECTION 10

#1732847656522

588-482: Is a name used by various resistance organisations in Ireland throughout the 20th and 21st centuries. Organisations by this name have been dedicated to anti-imperialism through Irish republicanism , the belief that all of Ireland should be an independent republic free from British colonial rule. The original Irish Republican Army (1919–1922) , often now referred to as the "old IRA", was raised in 1917 from members of

637-404: Is called Hooke's law , which is often presumed to apply up to the elastic limit for most metals or crystalline materials whereas nonlinear elasticity is generally required to model large deformations of rubbery materials even in the elastic range. For even higher stresses, materials exhibit plastic behavior , that is, they deform irreversibly and do not return to their original shape after stress

686-438: Is described by a stress–strain curve , which shows the relation between stress (the average restorative internal force per unit area) and strain (the relative deformation). The curve is generally nonlinear, but it can (by use of a Taylor series ) be approximated as linear for sufficiently small deformations (in which higher-order terms are negligible). If the material is isotropic , the linearized stress–strain relationship

735-491: Is no longer applied. For rubber-like materials such as elastomers , the slope of the stress–strain curve increases with stress, meaning that rubbers progressively become more difficult to stretch, while for most metals, the gradient decreases at very high stresses, meaning that they progressively become easier to stretch. Elasticity is not exhibited only by solids; non-Newtonian fluids , such as viscoelastic fluids , will also exhibit elasticity in certain conditions quantified by

784-409: Is one of the most prestigious competitions, attracting participants globally who demonstrate their accuracy and skill by aiming at various targets. Competitions and Events Types of Competitions Equipment Skills and Techniques Community and Culture Overall, slingshot sports blend tradition with modernity, making them an engaging and accessible activity for people of all ages. One of

833-416: Is path dependent) as well as conservative " hyperelastic material " models (for which stress can be derived from a scalar "elastic potential" function). A hypoelastic material can be rigorously defined as one that is modeled using a constitutive equation satisfying the following two criteria: If only these two original criteria are used to define hypoelasticity, then hyperelasticity would be included as

882-400: Is removed. Solid objects will deform when adequate loads are applied to them; if the material is elastic, the object will return to its initial shape and size after removal. This is in contrast to plasticity , in which the object fails to do so and instead remains in its deformed state. The physical reasons for elastic behavior can be quite different for different materials. In metals ,

931-506: Is said to be Cauchy-elastic if the Cauchy stress tensor σ is a function of the deformation gradient F alone: It is generally incorrect to state that Cauchy stress is a function of merely a strain tensor , as such a model lacks crucial information about material rotation needed to produce correct results for an anisotropic medium subjected to vertical extension in comparison to the same extension applied horizontally and then subjected to

980-462: The 2003 invasion of Iraq , Saddam Hussein released a propaganda video demonstrating slingshots as a possible insurgency weapon for use against invading forces. Slingshots have also been used by the military to launch unmanned aerial vehicles (UAVs). Two crew members form the fork, with an elastic cord stretched between them to provide power to launch the small aircraft. On the Battle of Marawi ,

1029-717: The 2019-2020 protests where they were used against the Hong Kong Police Force , by the Palestinians against Israeli forces . and by the Ukrainians during the Maidan Revolution in 2014. Slingshots have been used as military weapons, but primarily by guerrilla forces due to the easily available resources and technology required to construct one. Such guerrilla groups included the Irish Republican Army ; prior to

SECTION 20

#1732847656522

1078-699: The Deborah number . 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, these fluids may start to flow like a viscous liquid. 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. Typically, two types of relation are considered. The first type deals with materials that are elastic only for small strains. The second deals with materials that are not limited to small strains. Clearly,

1127-736: The Irish Volunteers and the Irish Citizen Army later reinforced by Irishmen formerly in the British Army in World War I , who returned to Ireland to fight against Britain in the Irish War of Independence . In Irish law, this IRA was the army of the revolutionary Irish Republic as declared by its parliament, Dáil Éireann , in 1919. In the century that followed, the original IRA was reorganized, changed and split on multiple occasions, to such

1176-411: The atomic lattice changes size and shape when forces are applied (energy is added to the system). 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. Hooke's law states that the force required to deform elastic objects should be directly proportional to

1225-406: The dimension L ⋅M⋅T . For most commonly used engineering materials, the elastic modulus is on the scale of gigapascals (GPa, 10 Pa). As noted above, for small deformations, most elastic materials such as springs exhibit linear elasticity and can be described by a linear relation between the stress and strain. This relationship is known as Hooke's law . A geometry-dependent version of the idea

1274-412: The actual (not objective) stress rate. Hyperelastic materials (also called Green elastic materials) are conservative models that are derived from a strain energy density function ( W ). A model is hyperelastic if and only if it is possible to express the Cauchy stress tensor as a function of the deformation gradient via a relationship of the form This formulation takes the energy potential ( W ) as

1323-455: The addition of a suitable rest, the slingshot can also be used to shoot arrows , allowing the hunting of medium-sized game at short ranges. While commercially made slingshots date from at latest 1918, with the introduction of the Zip-Zip, a cast iron model, it was not until the post– World War II years that slingshots saw a surge in popularity, and legitimacy. They were still primarily home-built;

1372-402: The chance of a fork end failure is to utilize a tapered band, thinner at the pouch end, and thicker and stronger at the fork end. Designs that use loose parts at the fork are the most dangerous, as they can result in those parts being propelled back towards the shooter's face, such as the ball attachment used in the recalled Daisy "Natural" line of slingshots (see image). The band could slip out of

1421-461: The configuration which minimizes the free energy, subject to constraints derived from their structure, and, depending on whether the energy or the entropy term dominates the free energy, materials can broadly be classified as energy-elastic and entropy-elastic . As such, microscopic factors affecting the free energy, such as the equilibrium distance between molecules, can affect the elasticity of materials: for instance, in inorganic materials, as

1470-444: The dangers inherent in slingshots is the high probability that the bands will fail. Most bands are made from latex , which degrades with time and use, causing the bands to eventually fail under load. Failures at the pouch end are safest, as they result in the band rebounding away from the user. Failures at the fork end, however, send the band back towards the shooter's face, which can cause eye and facial injuries. One method to minimize

1519-426: The distance of deformation, regardless of how large that distance becomes. This is known as perfect elasticity , in which a given object will return to its original shape no matter how strongly it is deformed. This is an ideal concept only; most materials which possess elasticity in practice remain purely elastic only up to very small deformations, after which plastic (permanent) deformation occurs. In engineering ,

Slingshot - Misplaced Pages Continue

1568-422: The elasticity of a material is quantified by the elastic modulus such as the Young's modulus , bulk modulus or shear modulus which measure the amount of stress needed to achieve a unit of strain ; a higher modulus indicates that the material is harder to deform. The SI unit of this modulus is the pascal (Pa). The material's elastic limit or yield strength is the maximum stress that can arise before

1617-489: The equilibrium distance between molecules at 0 K increases, the bulk modulus decreases. The effect of temperature on elasticity is difficult to isolate, because there are numerous factors affecting it. For instance, the bulk modulus of a material is dependent on the form of its lattice , its behavior under expansion , as well as the vibrations of the molecules, all of which are dependent on temperature. Irish Republican Army The Irish Republican Army ( IRA )

1666-683: The first issue on any Irish organisation's agenda was "the split". For the IRA, that has often been the case. The first split came after the Anglo-Irish Treaty in 1921, with supporters of the Treaty forming the nucleus of the National Army of the newly created Irish Free State , while the anti-treaty forces continued to use the name Irish Republican Army . After the end of the Irish Civil War (1922–23),

1715-411: The hands of a skilled user. Firing projectiles, such as lead musket balls, buckshot , steel ball bearings , air gun pellets , or small nails , a slingshot was capable of taking game such as quail, pheasant, rabbit, dove, and squirrel. Placing multiple balls in the pouch produces a shotgun effect (even though not very accurate), such as firing a dozen BBs at a time for hunting small birds. With

1764-445: The hyperelastic model may be written alternatively as Linear elasticity is used widely in the design and analysis of structures such as beams , plates and shells , and sandwich composites . This theory is also the basis of much of fracture mechanics . Hyperelasticity is primarily used to determine the response of elastomer -based objects such as gaskets and of biological materials such as soft tissues and cell membranes . In

1813-431: The inherent elastic properties of a material as a resistance to deformation under an applied load. The various moduli apply to different kinds of deformation. For instance, Young's modulus applies to extension/compression of a body, whereas the shear modulus applies to its shear . Young's modulus and shear modulus are only for solids, whereas the bulk modulus is for solids, liquids, and gases. The elasticity of materials

1862-474: The neck of a plastic bottle, or a small pipe. The projectile is inserted through the tube and into the cut balloon, and the user stretches the balloon to launch the projectile. These so-called "balloon guns" are sometimes made as a substitute to ordinary slingshot, and are often used to create the "shotgun" effect with several projectiles fired at once. In modern times the slingshot has been used by civilians against governments. Examples of this are Hong Kong during

1911-408: The onset of plastic deformation. Its SI unit is also the pascal (Pa). When an elastic material is deformed due to an external force, it experiences internal resistance to the deformation and restores it to its original state if the external force is no longer applied. There are various elastic moduli , such as Young's modulus , the shear modulus , and the bulk modulus , all of which are measures of

1960-415: The possibility of large rotations, large distortions, and intrinsic or induced anisotropy . For more general situations, any of a number of stress measures can be used, and it is generally desired (but not required) that the elastic stress–strain relation be phrased in terms of a finite strain measure that is work conjugate to the selected stress measure, i.e., the time integral of the inner product of

2009-537: The presence of fractures affects the Young and the shear moduli perpendicular to the planes of the cracks, which decrease (Young's modulus faster than the shear modulus) as the fracture density increases, indicating that the presence of cracks makes bodies brittler. Microscopically , the stress–strain relationship of materials is in general governed by the Helmholtz free energy , a thermodynamic quantity . Molecules settle in

Slingshot - Misplaced Pages Continue

2058-484: The same internal energy. Note that the second criterion requires only that the function G {\displaystyle G} exists . As detailed in the main hypoelastic material article, specific formulations of hypoelastic models typically employ so-called objective rates so that the G {\displaystyle G} function exists only implicitly and is typically needed explicitly only for numerical stress updates performed via direct integration of

2107-518: The second type of relation is more general in the sense that it must include the first type as a special case. For small strains, the measure of stress that is used is the Cauchy stress while the measure of strain that is used is the infinitesimal strain tensor ; the resulting (predicted) material behavior is termed linear elasticity , which (for isotropic media) is called the generalized Hooke's law . Cauchy elastic materials and hypoelastic materials are models that extend Hooke's law to allow for

2156-431: The slot in which it rested, and the hard ball in the tube resulted in cases of blindness and broken teeth. Daisy models using plain tubular bands were not covered in the recall, because the elastic tubing does not cause severe injuries upon failure. Another big danger is the fork breakage; some commercial slingshots made from cheap zinc alloy may break and severely injure shooters' eyes and face. Many jurisdictions prohibit

2205-504: The soldiers of the Philippine Army's elite Scout Rangers were observed using slingshots with grenades as an improvised mortar to attack Maute and Abu Sayyaf forces. Slingshots, often recognized as tools or toys, are also utilized in various organized sports around the world. Competitive slingshot shooting, or catapult shooting, is gaining popularity, with events held in countries like Spain, Italy, and China. The Slingshot World Cup

2254-413: The stress measure with the rate of the strain measure should be equal to the change in internal energy for any adiabatic process that remains below the elastic limit. The SI unit for elasticity and the elastic modulus is the pascal (Pa). This unit is defined as force per unit area, generally a measurement of pressure , which in mechanics corresponds to stress . The pascal and therefore elasticity have

2303-402: The use of arm-braced slingshots. For example, New York Penal law 265.01 defines it as a Class-4 misdemeanor, and in some states of Australia they are also a prohibited weapon. Elasticity (physics) In physics and materials science , elasticity is the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force

2352-422: Was first formulated by Robert Hooke in 1675 as a Latin anagram , "ceiiinosssttuv". He published the answer in 1678: " Ut tensio, sic vis " meaning " As the extension, so the force ", a linear relationship commonly referred to as Hooke's law . This law can be stated as a relationship between tensile force F and corresponding extension displacement x {\displaystyle x} , where k

2401-577: Was suitable for hunting, with a draw weight of up to 200 newtons (45 pounds-force ), and was available with an arrow rest. The National Slingshot Association was founded in the 1940s, headquartered in San Marino, California . It organised slingshot clubs and competitions nationwide. Despite the slingshot's reputation as a tool of juvenile delinquents, the NSA reported that 80% of slingshot sales were to men over 30 years old, many of them professionals. John Milligan,

#521478