Manipal Medical Manipal Medical Solved Paper-2003

  • question_answer
    When the kinetic energy of a body executing S.H.M. is 1/3 of the potential energy. The displacement of the body is\[x\]percent of the amplitude, where\[x\] is:

    A)  33             

    B)  87

    C)  67             

    D)  50

    Correct Answer: B

    Solution :

     The relation for kinetic energy of S.H.M. is given by \[=\frac{1}{2}m{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})\]           ...(1) Potential energy is given by \[=\frac{1}{2}m{{\omega }^{2}}{{y}^{2}}\]                  ...(2) Now for the condition of question and from eqs. (1) and (2) \[\frac{1}{2}m{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})=\frac{1}{3}\times \frac{1}{2}m{{\omega }^{2}}{{y}^{2}}\] Or \[\frac{4}{6}m{{\omega }^{2}}{{y}^{2}}=\frac{1}{2}m{{\omega }^{2}}{{a}^{2}}\] Or \[{{y}^{2}}=\frac{3}{4}{{a}^{2}}\] So, \[y=\frac{a}{2}\sqrt{3}=0.866\,a\] \[\approx 87%\]of amplitude


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