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BITSAT 2009
Exam
BITSAT
Year
2009
Subject
Physics
Chapter
Work, Power and Energy

BITSAT 2009 · Physics · Work, Power and Energy

A chain of mass M is placed on a smooth table with 1 / n of its...

A chain of mass M\mathrm{M} is placed on a smooth table with 1/n1 / \mathrm{n} of its length L\mathrm{L} hanging over the edge. The work done in pulling the hanging portion of the chain back to the surface of the table is

Options

  1. AMgL/n\mathrm{MgL} / \mathrm{n}
  2. BMgL/2n\mathrm{MgL} / 2 \mathrm{n}
  3. CMgL/\mathrmn2\mathrm{MgL} / \mathrmn^{2}
  4. DMgL/2\mathrmn2\mathrm{MgL} / 2 \mathrmn^{2}

Correct answer

D. MgL/2\mathrmn2\mathrm{MgL} / 2 \mathrmn^{2}

Step-by-step solution

W=\quad \mathrm{W}= change in PE\mathrm{PE} of COM\mathrm{COM} of hanging part =MngL2n=MgL2\mathrmn2\frac{\mathrm{M}}{\mathrm{n}} \mathrm{g} \frac{\mathrm{L}}{2 \mathrm{n}}=\frac{\mathrm{MgL}}{2 \mathrmn^{2}}
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