Choose the correct statements from the following:

Options

A. Steel is more elastic than rubber.
B. The stretching of a coil spring is determined by the Young's modulus of the wire of the spring.
C. The frequency of a tuning fork is determined by the shear modulus of the material of the fork.
D. When a material is subjected to a tensile (stretching) stress the restoring forces are caused by interatomic attraction.

Answer

A

Explanation

Statement (a) is correct because the Young's modulus of steel is greater than that of rubber.
Statement (b) is incorrect. If a spring is stretched, both the total length of the wire in the coil and the volume of the wire do not change. Only the shape of the coils of the wire undergoes a change. Hence, it is the shear modulus that determines the stretching of the coil.
Statement (c) is also incorrect. The bending moment of the prongs of a tuning fork is determined by the Young's modulus of the material. Hence, the restoring force on the prongs depends on Young's modulus which determines the frequency of the fork. Statement (d) is correct. When the material is not subjected to any stress, its atoms are in their normal (equilibrium) positions.
When a tensile stress is applied, the separation `R` between the atom becomes greater than the equilibrium separation `R_(0)`. For `RgtR_(0)` the interactomic forces are attractive.