Question:

When two springs A and B with force constants \(k_A\) and \(k_B\) are stretched by the same force, then the respective ratio of the work done on them is

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For same force, softer spring (smaller \(k\)) stores more energy.
Updated On: May 8, 2026
  • \(k_B : k_A\)
  • \(k_A : k_B\)
  • \(k_A k_B : 1\)
  • \(\sqrt{k_B} : \sqrt{k_A}\)
  • \(\sqrt{k_A} : \sqrt{k_B}\)
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The Correct Option is A

Solution and Explanation

Concept: Work done in stretching a spring: \[ W = \frac{1}{2}kx^2 \] Also, from Hooke’s law: \[ F = kx \Rightarrow x = \frac{F}{k} \]

Step 1:
Substitute \(x = \frac{F}{k}\) into work formula. \[ W = \frac{1}{2}k \left(\frac{F}{k}\right)^2 \]

Step 2:
Simplify expression. \[ W = \frac{1}{2}k \cdot \frac{F^2}{k^2} = \frac{F^2}{2k} \]

Step 3:
Relation between work and spring constant. \[ W \propto \frac{1}{k} \]

Step 4:
Take ratio. \[ \frac{W_A}{W_B} = \frac{1/k_A}{1/k_B} = \frac{k_B}{k_A} \]

Step 5:
Conclusion. \[ \boxed{k_B : k_A} \]
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