Question

When a body undergoes a linear tensile strain if they experience a lateral contraction also. The ratio of lateral contraction to longitudinal strain is known as
A. Young’s modulus
B. Bulk modulus
C. Poisson’s law
D. Hooke’s law

Answer 1

Hint: All the terms given as options are related to elasticity. Elasticity is the property of a solid substance to return to its original or initial shape and size when the forces deforming them are removed. All these terms give the relation between the forces applied on a molecule and the change in the shape and size of the molecule due to that force. To answer this question, you should have knowledge of these elasticity terms.

Complete answer:
Young’s modulus: Young’s modulus is a coefficient which relates tensile stress to tensile strain. It can be defined as the ratio of tensile stress to tensile strength. For a perfectly rigid body strain is zero. Hence, it’s value for a perfectly rigid body is infinite.
Bulk modulus: Bulk modulus is a coefficient which relates stress to compressive strain. It can be defined as the ratio of increase in pressure to volumetric strain. It is also known as Modulus of rigidity.
Poisson’s law: Poisson’s law is the law which gives Poisson’s ratio. Poisson’s ratio is the ratio of lateral strain to axial stress. It can also be defined as the ratio of lateral contraction to longitudinal strain when force is applied. For most of the materials, the value of Poisson’s ratio lies between 0 and 0.5.
Hooke’s law: Hooke’s law is the law of elasticity. It states that the force required to extend or compress a spring by some distance is proportional to that distance. Hooke's law holds true for various situations where an elastic body is deformed by some force. Musician plucking the strings of a guitar is one of the many situations where Hooke’s law holds true.
Hence, the ratio of lateral contraction to longitudinal strain is known as Poisson’s law.

So, the correct answer is “Option C”.

Note:
Students should know each modulus and their properties to answer these types of questions. Young's modulus and Shear modulus are applicable for solids while the Bulk modulus is only applicable to liquids. Due to Young's modulus and Shear modulus the shape of the material changes. While, the Bulk modulus causes change in the volume of the object. Higher the value of Young’s modulus, greater is the capacity of material to withstand the change in length.