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GATE 2020 ME (ME2) – Question 41

Machine Design · Shafts and springs · 2 marks · Multiple choice

A helical spring has spring constant k. Wire diameter, spring diameter and number of coils are all doubled. Find the new spring constant.

  1. k/2
  2. k
  3. 8k
  4. 16k

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Show answer and explanation

Correct answer: (B) k

Explanation

For a close-coiled spring $k=Gd^4/(8D^3N)$. Doubling d,D,N changes stiffness by2⁴/(2³×2)=1. Therefore the new stiffness is **k,B**. All three geometric changes must be included.