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

NEET 2009 · Physics · Work, Power and Energy

A block of mass M is attached to the lower end of a vertical...

A block of mass MM is attached to the lower end of a vertical spring. The spring is hung from a ceiling and has force constant value k\mathrm{k}. The mass is released from rest with the spring initially unstretched. The maximum extension produced in the length of the spring will be :

Options

  1. AMg/2k\mathrm{Mg} / 2 \mathrm{k}
  2. BMg/k\mathrm{Mg} / \mathrm{k}
  3. C2Mg/k2 \mathrm{Mg} / \mathrm{k}
  4. D4Mg/k4 \mathrm{Mg} / \mathrm{k}

Correct answer

C. 2Mg/k2 \mathrm{Mg} / \mathrm{k}

Step-by-step solution

Loss in grav. PE=\mathrm{PE}= gain in spring PE\mathrm{PE} At maximum elongation Mgx=12kx2x=2Mgk\begin{aligned}\mathrm{Mgx}& =\frac{1}{2} \mathrm{kx}^2 \\ \mathrm{x}& =\frac{2 \mathrm{Mg}}{\mathrm{k}} \end{aligned}
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