Short Answer:

Elasticity is the property of a material by which it regains its original shape and size after the removal of the external force that caused deformation. It means that when a force is applied to stretch or compress a material, it temporarily changes its shape, but once the force is removed, the material returns to its original form.

This property is very important in engineering materials like steel and rubber, as it helps them resist deformation and maintain their structure under applied loads. The measure of elasticity of a material is given by modulus of elasticity, which shows how stiff or flexible the material is.

Detailed Explanation:

Elasticity

Elasticity is a fundamental mechanical property of materials that describes their ability to return to their original shape and size after being deformed by an external force. When a material such as metal, wood, or rubber is subjected to forces like tension, compression, or bending, it undergoes a change in its dimensions. This change is known as deformation. If the deformation disappears after the removal of the applied force, the material is said to be elastic.

For example, when you stretch a rubber band, it becomes longer. As soon as you release it, the rubber band quickly returns to its original length. This is a clear example of elasticity. Similarly, in structures like bridges and machines, materials experience different types of loads. The materials used must be elastic enough to come back to their normal shape after the load is removed, ensuring safety and durability.

The concept of elasticity was first studied by Robert Hooke, who discovered that within the elastic limit, the amount of deformation produced in a material is directly proportional to the applied load. This relationship is known as Hooke’s Law, which can be expressed as:
Stress ∝ Strain (within elastic limit).

Elasticity depends on several factors such as the type of material, temperature, and the amount of load applied. For instance, metals like steel and copper are more elastic compared to lead or concrete. Also, as the temperature of a material increases, its elasticity generally decreases because the internal molecular bonds become weaker.

The measure of elasticity is expressed through a property called the Modulus of Elasticity or Young’s Modulus. It represents the ratio of stress to strain within the elastic limit and indicates how resistant a material is to deformation. A higher value of modulus of elasticity means the material is more rigid and less likely to deform under load.

Elastic materials play a vital role in mechanical and structural engineering. In machine design, for example, springs, beams, shafts, and other parts must be made from materials that can temporarily deform under load and then recover. Elastic behavior also helps in absorbing shocks and vibrations in vehicles and machinery, increasing their lifespan.

Elasticity is not permanent for all materials; every material has an elastic limit. If the applied stress goes beyond this limit, the material will not return to its original shape, leading to plastic deformation or even failure. Therefore, engineers always design components such that the stress remains within the elastic limit to ensure safe operation.

There are also different types of elasticity depending on the way the force is applied:

1. Linear Elasticity: The material returns to its original length when the load is removed (like a stretched wire).
2. Volumetric Elasticity: The material changes in volume when compressed or stretched (like air in a balloon).
3. Shear Elasticity: The material deforms in shape but not in volume (like a rubber sheet under tangential force).

In summary, elasticity is an essential concept in the field of mechanics and material science. It allows engineers to predict how materials will behave under different loads, ensuring that machines, buildings, and vehicles are both strong and safe. Understanding elasticity helps in selecting suitable materials that can withstand forces without permanent damage.

Conclusion:

Elasticity is the property that enables materials to regain their original shape after deformation. It ensures the safe functioning of machines and structures by preventing permanent damage. Materials like steel and rubber show excellent elastic behavior within limits. Knowing the elasticity of materials is vital in mechanical design to maintain strength, reliability, and efficiency in engineering applications.