AFMC AFMC Solved Paper-2011

  • question_answer
    When a spring is extended by 2 cm energy stored is 100 J. When extended by further 2 cm, the energy increases by

    A) 400 J                                     

    B) 300 J

    C) 200 J                                     

    D) 100 J

    Correct Answer: B

    Solution :

    Potential energy stored in the spring is given \[U=\frac{1}{2}k{{x}^{2}}\] \[\therefore \]  \[\frac{{{U}_{1}}}{{{U}_{2}}}={{\left( \frac{{{x}_{1}}}{{{x}_{2}}} \right)}^{2}}\] or    \[\frac{100}{{{U}_{2}}}=\frac{{{(2)}^{2}}}{{{(4)}^{2}}}\] or    \[{{U}_{2}}=400\,J\]               \[\therefore \]  Potential energy increases by \[400-100=300\text{ }J\]


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