Question

The young’s modulus of air is:
(A) Infinity
(B) more than 1 but not infinity
(C) less than 1 but not zero
(D) zero

Answer 1

Hint: Using young’s modulus formula , find the relation between stress and strain. Under the elastic region, understand how air molecules move when they experience a stress and compare it with solid molecules to conclude your solution.

Complete step by step solution:
Young’s modulus is the ratio between the stress and strain. This implies that stress is directly proportional to strain. In a solid molecule under the elastic region, the molecules are tightly packed and hence the force of attraction between the molecules . Thus when a stress is applied on a solid , the particles tend to attract each other to retain its shape.
Therefore young’s modulus for solid will always be greater than 1.
However, in air and gases, molecules are very loosely packed , which means that there will be very minimum force of attraction. When a stress is applied to gas molecules, there will be very minimal strain produced on the molecules, but it doesn’t mean that no strain will be produced on the body.
Understanding this concept, when we apply the same in young’s modulus relation, we get to know that young’s modulus Y will not be zero rather it won’t exceed 1.
Therefore, young’s modulus of air is less than 1 but not zero.

Hence, Option (c) is the right answer for the given question

Note:
Young’s modulus or also called as modulus of elasticity, is a property of material that estimates the tensile stiffness or its ability to resist compression and elongation when a stress is applied on it. It is measured in Pascals.