In the light of the above statements, choose the most appropriate answer from the options given below:
- Both (A) and (R) are true and (R) is the correct explanation of (A)
- Both (A) and (R) are true and (R) is not the correct explanation of (A)
- (A) is true but (R) is false
- (A) is false but (R) is true
Answer
(3) (A) is true but (R) is false
Solution
When a coil spring is stretched, its wire is twisted; the length and volume of the wire do not change, only its shape changes. Hence the stretching of a spring is governed by the shear modulus (modulus of rigidity) of its material. Assertion is true.
Steel has a much larger elastic modulus and tensile strength than copper, so a steel spring is stronger than a copper spring of the same dimensions. Reason is false.
(A) is true but (R) is false.
Answer: (3)