Elasticity is a very interesting word. It came into everyday vocabulary from science, and has acquired a meaning that is totally opposite to the original meaning.
Elasticity According To Physics
Elasticity, as everyone understands, is the property of being stretched and restored. In physics they have discovered that almost all solids have this property. If they are stretched (with a certain limit, of course) they lengthen. On removing the force, they go back to their original shape.
In fact, stretching is not the only thing that can be done. One can stretch, shear, compress, and do many things with force to alter the shape of a solid body. Each time the body returns to the original shape and position after this force is removed. This property of materials to yield to deforming forces, only to come back to the normal shape after the forces are removed is called "elasticity".
Liquids and gases have no permanent shape, and they do not go back to the original shape because they have no shape of their own. However, they can be compressed to decrease their volume. As soon as the forces of compression are removed, they go back to their original volume. Thus even liquids and gases do exhibit what is called volume-elasticity.
The Value Of Elasticity
Physics tries to put everything into measurable quantities. This quantification helps accurate comparison of two things. For example, if the elasticity of different materials is quantified, just a look at those quantities will show which material is more elastic and which one is less.
To quantify elasticity, physics defines elasticity as "resistance to change". The greater the resistance to change, the greater is the elasticity of the material and the faster it comes back to its original shape or configuration when the deforming force is removed. By this definition, steel is more elastic than rubber because steel comes back to its original shape faster than rubber when the deforming forces are removed.
Elasticity In Physics And In Common Life
In common life we label a substance as more elastic if it can be stretched more than others. In physics a substance is labelled more elastic if it offers greater resistance to deformation than other bodies, so that it can be stretched less than others.
The fundamental difference between the definition in physics and definition in common life should always be kept in mind when one speaks of elasticity. Else one is likely to leave his listeners/readers totally confused. Please remember, the more a body can be stretched or deformed without breaking it, the more elastic it is called in common language. Coming to physics, the less a body can be stretched or deformed without breaking it, the more elastic it is considered in physics.
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