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Question: Answered & Verified by Expert
A wooden stick of length L, radius R and density ρ has a small metal piece of mass m (of negligible volume) attached to its one end. Find the minimum value for the mass m (in terms of given parameters) that would make the stick float vertically in stable equilibrium in a liquid of density σ .
PhysicsMechanical Properties of FluidsJEE Main
Options:
  • A 2πR2Lρσρ-1
  • B πR2Lρ2σρ-1
  • C πR2Lρσρ-1
  • D πR2Lρσ2ρ-1
Solution:
2795 Upvotes Verified Answer
The correct answer is: πR2Lρσρ-1
M+mg=πR2hσg  .... (i)

M=πR2Lρ

The height of center of mass from bottom

ML/2+m×0m+M=ML2m+M



For rotatory equilibrium and for minimum m, thus should be equal to h/2

 h2=ML2m+M .... (ii)

  h=ML2m+M;m=πR2Lσρ-πR2Lρ    =πR2Lρσρ-1

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