Question

The Young’s modulus of a perfectly rigid body is
A. Unity
B. Zero
C. Infinity
D. Some finite non-zero constant

Answer 1

Hint: Before attempting this question, one should have prior knowledge about the concept of young’s modulus and also remember that for a perfectly rigid body strain is equal to 0, using this information will help you to approach the solution of the question.

Complete answer:
In the given statement we have perfectly rigid body
We know that a perfectly rigid body is defined as the solid body which doesn’t show any deformation i.e. strain is equal to zero
We know that the formula for Young’s modulus is given as; ${\text{Young modulus = }}\dfrac{{stress}}{{strain}}$
Let x be the stress experienced by the perfectly rigid body
Now substituting the values in the formula of young’s modulus we get
${\text{Young modulus = }}\dfrac{x}{0}$
We know that whenever the denominator is zero
The result is always not-defined or infinity
Therefore, Young’s modulus for perfectly rigid body will be infinity

So, the correct answer is “Option C”.

Note:
In the above solution we came across the term “Young’s modulus” which can be explained as the term which defines the mechanical properties of the material such as the maximum force a material can hold its configuration. Formula of Young’s modulus is given as ${\text{Young modulus = }}\dfrac{{stress}}{{strain}}$ here stress is explained as force acting on the body per unit area whereas strain is the term which tells the amount of material is stretched or deformed.