Mechanical Properties of solids NCERT Solutions Class 11 Physics - Solved Exercise Question 9.4

Question 9.4:
Read the following two statements below carefully and state, with reasons, if it is true or false.
(a) The Young’s modulus of rubber is greater than that of steel;
(b) The stretching of a coil is determined by its shear modulus.
Solution:
(a) False
Young’s modulus, Y = Stress / Strain
For a constant stress: Y ∝ (1 / Strain)
Hence, Young’s modulus for rubber is less than it is for steel.

(b) True
Shear modulus is the ratio of the applied stress to the change in the shape of a body. The stretching of a coil changes its shape. Hence, shear modulus of elasticity is involved in this process.

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