Elastic

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Template:Wiktionary Elastic may refer to:

• Elasticity (economics)
• in Materials Science the word elastomer refers to a material which is very elastic, like rubber. The word elastic is often used colloquially to refer to an elastomeric material such as rubber or cloth/rubber combinations.
  • holding things together, e.g. with a rubber band
  • flexibly moving something over a thick to a thin part, as in clothing put on over the head, hips, hands, feet, and elastic necklaces, bracelets, watcharmbands. An alternative in many of these cases (not for socks) is a closing device such as buttons, a zipper, laces, Velcro, a buckle, a snap
  • flexibly making airtight or fluidtight connections as in a hose or condom
  • flexibly cushioning (a shock absorber) as with tires and for the soles of shoes, and under the legs of chairs, under vibrating equipment, on a door or door-post, on bumper cars, etc.
  • flexibly filling a volume of stretchable material with gas or fluids as in balloons and for use in medicine
  • for reducing downward speed gradually as in bungee jumping, and then pulling one up again
  • for accelerating an object such as slingshot, bow (weapon)

For some elastic use applications a metal spring is an alternative.

In some of the materials applications the flexibility is needed but not the elastic force. In that case, when a large flexibility is needed for a large surface, a folding wall is an alternative connections between railroad cars and in articulated buses, and in an accordion.

• In solid mechanics, the adjective elastic characterises both collisions between, and deformations of, physical objects.

A collision is perfectly elastic if the total pre-collision (initial) kinetic energy of a system is equal to the total post-collision (final) kinetic energy of the system. In other words, a collision is perfectly elastic only so long as no kinetic energy of the objects within the system is converted to other forms of energy during the collision, such as heat energy or sound energy. To date, no collision has ever been observed to be truly elastic. Even in the collision between two electrons, which is the most elastic collision currently known, an infinitesimal portion of the initial kinetic evergy is converted to other forms of energy.

A frequent cause of highly inelastic collisions occurs when one or more of the objects suffers a plastic deformation.

The deformation of a solid is part of the study of solid mechanics. In solid mechanics, a material behaves elastically if it changes shape due to an applied load, and that when the load is removed, recovers its original shape. According to solid mechanics theory, every material will change shape when loads are applied to it (even very small loads). Furthermore, every material will undergo elastic deformation as long as the loads are kept under a certain limit. This limit is known as the elastic limit or the yield strength of the material, and is one way of defining its strength.

Elastic deformation can be either linear or nonlinear. In linear elasticity, the elastic deformation is proportional to the applied load. The elasticity of a solid is inversely proportional to its stiffness. Stiffness, when corrected for the dimensions of the solid, becomes modulus of elasticity, which is an intensive property of the material. The stiffness of a structure is of principle importance in many engineering applications, so modulus of elasticity is often one of the primary properties considered when selecting a material. A high modulus of elasticity is sought when deflections are undesirable, while a low modulus of elasticity is required when flexibilty is needed.

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