# Elasticity

What is elasticity? As we hear the word ‘elastic’, an image of a rubber band or a very fit & flexible dancer comes into our mind. Many people are stuck with the idea that rubber band is one of the most elastic stuffs around us. Is this true or just a myth? Here we will first try to discuss “what is elasticity” or the definition of elasticity. We must have observed that to change or deform shape or size of an object, some amount of force is to be applied. Elasticity is all about regaining the original shape and size of that object as and when the force is removed. We will also discuss on that topic that many people continuously argue on – what is more elastic rubber or iron.

## Elasticity definition

The property, by which an object tends to regain its original size and shape when the applied force on it is removed, is known as Elasticity.
The deformation caused is called elastic deformation.

If we apply force to a lump of mud, it won’t show any tendency to regain its previous shape. We find it deformed permanently.

Such substances which don’t show any tendency of elasticity or in other words, substances with no tendency to regain original shape and size as the force is removed are called Plastic. And this property is known as plasticity.

## What is more elastic rubber or iron?

The greater is the elasticity of the material, the greater would be its tendency to resist deformation and the greater would be its chance to get back to its original shape or size when the deforming force is removed.

Clearly we can see with equal amount of force being applied on equal area of both, iron rod will have much less deformity and much more chance to get back its original shape and size in much lesser time than the rubber band. So Iron rod is a definite winner here. Therefore, we can say that Iron is more elastic than rubber. In other words, iron shows elasticity while rubber exhibits plasticity.

## Elastic Behaviour – causes

Each atom is surrounded by neighbouring atoms; similarly each molecule has its neighbouring molecules surrounding it.

Atoms are bounded together by interatomic forces; similarly molecules are bounded by intermolecular forces.

All these stay in a stable equilibrium position.

When a force is applied the solid is deformed. the atoms/molecules are displaced from their equilibrium positions and interatomic and intermolecular distances change.

When the deforming force is removed, the interatomic forces try to drive them back to their original positions. If it is successful then the body regains its original shape and size.

### Spring ball Model

Elastic behaviour of solids can be well explained by Spring Ball Model. Here Atoms are modelled with balls and interatomic forces are represented with springs. If we try to displace a ball from its equilibrium position, then the spring system tries to restore the ball back to its original position.

Related: Learn more about Stress and Strain, different types of stress and strain, Hooke’s Law, Modulus of Elasticity etc here: Hooke’s law

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