Under the same load, wire A having length and cross section stretches uniformly by the same amount as another wire B of length and a cross section of . The ratio of the Young's modulus of wire A to that of wire B will be:
- A
- B
- C
- D
Under the same load, wire A having length and cross section stretches uniformly by the same amount as another wire B of length and a cross section of . The ratio of the Young's modulus of wire A to that of wire B will be:
Correct answer:B
Standard Method
Given: Same load acts on both wires and both wires have the same elongation. For wire A, and . For wire B, and .
Find: The ratio .
Young's modulus is given by
where is the load, is the length, is the cross-sectional area, and is the elongation.
Since the load and elongation are the same for both wires,
Substituting the given values,
Therefore, the ratio of the Young's modulus of wire A to wire B is . The correct option is B.
Using is incorrect because the area terms get cross-multiplied when forming the ratio from . Write the full ratio first and then cancel the common terms carefully.
Assuming equal elongation means equal strain is incorrect because strain is , and the lengths of the two wires are different. Here only the elongation is same, not the strain.
Ignoring that the same load acts on both wires is wrong because cancellation of is essential in the ratio. Keep track of which quantities are common before substituting values.
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