Question

The only elastic modulus that applies to fluid is
A. Young’s Modulus
B. Shear Modulus
C. Modulus of rigidity
D. Bulk Modulus

Answer 1

Hint: The stress produced in the body is directly proportional to the strain produced in the same body, according to Hooke's law. We get a constant when we remove the proportionality sign. This constant varies depending on the medium in question. This constant is known as the Bulk modulus of elasticity for liquids.

Complete answer:
According to Hooke's law, the amount of stress developed in a body is proportional to the amount of strain developed in the same body. When the proportionality sign is removed, we get an elasticity constant. Young's modulus of elasticity is the name given to this constant in solids. The stain used for solids can be linear, area, or volumetric strain. This strain is always the volumetric strain in fluids. Bulk modulus is the proportionality constant in the case of fluids.
From the definition we know, all the elastic coefficients except bulk modulus deals with change in shape, the elastic material.
For liquid, we know that they do not have any exact shape, they acquire the shape of the container.
$BulkModulus={\displaystyle \frac{Volumestress}{Volumestrain}}$
So, only Bulk Modulus deals with change in volume and can be applied to fluids.
Hence, the correct option is: (D) Bulk Modulus

Note:
It should be noted that when dealing with liquids, another term is used. This is referred to as the fluid's rigidity. It is defined mathematically as the reciprocal of the Bulk modulus of elasticity. It is defined as a body's tendency to remain rigid when subjected to external forces.