The Probert Encyclopaedia of Science & Technology

ELASTICITY

Elasticity is the property in virtue of which bodies resist change of volume and change of shape, and recover their former figure or state after external pressure, tension, or distortion. The former is called elasticity of volume, the latter elasticity of shape. The name Compressibility is also used in connection with the elasticity of volume; and Rigidity, or resistance to change of shape, in connection with the latter. Fluids possess no rigidity whatever;. they offer no permanent resistance to change of shape; while a solid body, unless it is distorted beyond certain limits, called the limits of elasticity, tends to return to its original form. Both fluids and solids possess elasticity of volume, and tend to resume their original volume after compression. The elasticity of volume of the former is perfect; whatever compression they have been subjected to, they return under the same conditions of temperature to precisely their original volumes when the forces of compression are removed. In the case of solids there are limits to their elasticity of volume as well as to their elasticity of form; thus gold may be made permanently denser by hammering. There is one law of elasticity, the celebrated law of Hooke - Ut Tensio sic Vis, which translated into the modern language of elasticity states - Strain is proportional to stress; or, in other words, whatever be the nature of the distortion the amount of it is proportional to the stress that produces it. This law is only considered as applicable so long as we do not go beyond the limits of elasticity. Also of relevance to elasticity is Boyle's Law, which deals with gasses.
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