6.1 Deformation of Solids
We have observed that an external force applied on an object can change its size or shape. Such a force is known as a deforming force.
For example, an appropriate force applied to a spring can increase its length (called extension) or cause compression, thus reducing its length. If this force is removed, the spring will restore its original size and shape. Similarly, a stretched rubber strip or band comes back to its original shape and size on removing the applied force.
When a tennis ball is hit by a racket, the shapes of the tennis ball and racket strings are distorted or deformed. They regain their original shape after the ball bounces off the racket.
An object is said to be elastic if, after removal of the deforming force, it restores its original size and shape. This property of the material is known as elasticity. Due to this property, we can determine the strength of a material and the deformation produced under the action of a force.
Most materials are elastic up to a certain limit known as the elastic limit. Beyond the elastic limit, the change becomes permanent. The object or material does not regain its original shape or size even after the removal of the deforming force.
lightbulbFor Your Information! Some materials such as clay dough or plasticine do not return to their original shape after the removal of the deforming force. They are known as inelastic materials.