Question

Among the following, which is the least elastic material?
A. Steel
B. Iron
C. Copper
D. Rubber

Answer 1

This question can be addressed based on the property Elastic Limit. It is the stress applied per unit area for a solid without causing any permanent deformation. If a material is really elastic in scientific terms then the material should return to its original state when an applied stress is removed. Stress beyond a certain limit will always cause material to yield or flow.

Complete answer:
To understand the detailed solution we should be able to understand the stress-strain graph of a material.
When a material exceeds the elastic point in the stress-strain graph then they become vulnerable to breakage. They move into the plastic region which means they are no longer elastic.
Rubber has a very low elastic point and therefore is the least elastic of the given materials. The strain produced in rubber is much larger compared to all the other materials
Young’s modulus also plays a crucial role in determining the elasticity of a material. It is called the elastic modulus.
Young’s modulus is given as $\dfrac{{Stress}}{{Strain}}$
Higher the Young’s modulus the more elastic the material is.
The young’s modulus of the given materials are:
Steel, stainless AISI 302 - $180{\text{ }}GPa$
Iron - $210{\text{ }}GPa$
Copper - $117{\text{ }}GPa$
Rubber, small strain - $0.01{\text{ }} - {\text{ }}0.1{\text{ }}GPa$
Thus we can conclude that rubber is the least elastic material among the given materials.

So, the correct answer is “Option D”.

Note:
Knowing the elastic limit is very important when we consider materials for different purposes. The elastic flexibility of steel contributes to the higher wear resistance or stress loading ability. This is used in materials of support in engineering.