Question

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R). 
Assertion (A): The stretching of a spring is determined by the shear modulus of the material of the spring. 
Reason (R): A coil spring of copper has more tensile strength than a steel spring of same dimensions.
In the light of the above statements choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct and Statement II is incorrect
• D. Statement I is incorrect and Statement II is correct

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
When a helical spring is stretched, the wire of the spring undergoes twisting (torsion) rather than simple elongation. Torsion involves changes in shape, which relates to the shear modulus (modulus of rigidity).
Step 2: Detailed Explanation:
Evaluation of Assertion (A):
Stretching a spring causes a shearing strain in the wire. The resistance to this stretching depends on how much the material resists shearing. Thus, the shear modulus is the dominant elastic constant for springs.
Therefore, Assertion (A) is True.

Evaluation of Reason (R):
Tensile strength is a measure of the stress a material can withstand before breaking. Steel is well known to be more elastic and significantly stronger than copper. A steel spring will have a much higher tensile strength and a higher Young's modulus compared to a copper spring of the same dimensions.
Therefore, Reason (R) is False.
Step 3: Final Answer:
Assertion (A) is true but Reason (R) is false.