CMC Medical CMC-Medical VELLORE Solved Paper-2013

  • question_answer
    When the kinetic energy of a body executing SHM is I/3 of the potential energy. The displacement of the body is x per cent of the amplitude, where x is

    A)  33                         

    B)  87     

    C)  67                         

    D)  50

    Correct Answer: B

    Solution :

                    Kinetic energy\[=\frac{1}{2}m{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})\] Potential energy\[=\frac{1}{2}m{{\omega }^{2}}y\] \[=\frac{1}{2}m{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})\] \[=\frac{1}{3}\times \frac{1}{2}m{{\omega }^{2}}{{y}^{2}}\] \[\frac{4}{6}m{{\omega }^{2}}{{y}^{2}}=\frac{1}{2}m{{\omega }^{2}}{{a}^{2}}\] \[{{y}^{2}}=\frac{3}{4}{{a}^{2}}\] \[y=\frac{\sqrt{3}\,a}{2}-0.866\,a\]     \[=\] 87% of amplitude


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