Rubber is more elastic than Steel: Misconception
It is my entry to Suesa's Science Challenge. Thank you Suesa for this challenge.
What do you think which one is more elastic steel or rubber? The first thing that comes in our mind when we listen word elastic is rubber. So, it is obviously rubber. Wrong!! what could be the greatest lie of your life other than this?... It's not your fault, its due to general perception. Obviously, you are not satisfied with the answer, now you need explanation so, tathasthu.
Let me start with definition of elastic.[1]
capable of returning to its original length, shape, etc., after being stretched, deformed, compressed, or expanded:
It means if the object returns to its original position more easily then it is more elastic and vice versa.
When you stretch rubber, it stretches more so it takes time to return to its original state. But, if you stretch steel with same force, it stretches less. So, it is comes back to its original state more easily. So, it is more elastic.
In physics, there is physical parameter to measure this phenomenon called Young's modulus of elasticity. It is denoted by E. Numerically, it is given by;
E = normal stress/strain
Normal stress is the ratio of normal force to area of cross section. Normal means perpendicular to area.
Strain is the ratio of change in dimension by original dimension.
Consider arbitrary object with length 'L' and cross section area 'A'. Let normal force F is applied and its length increases by l. Then,
normal stress = F/A
strain = l/L
So, from definition;
E = (F/A)/(l/L)
E = FL/A l
To compare the elasticity, the change in length should be observed. Consider, two bars one of steel and other rubber of same length and cross sectional area. When same force F is applied, the change in length of rubber is greater than change in length of steel. But, when change in length is greater, the value of E will be less. So, rubber is less elastic than steel. This misconception kinda amuses me.
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