JEE Main & Advanced Physics Simple Harmonic Motion JEE PYQ-Simple Harmonic Motion

  • question_answer
    A particle executes simple harmonic motion with an amplitude of 5 cm. When the particle is at 4 cm from the mean position, the magnitude of its velocity in SI units is equal to that of its acceleration. Then, its periodic time in seconds is-            [JEE Main 10-Jan-2019 Evening]

    A)  \[\frac{4\pi }{3}\]         

    B)       \[\frac{3\,}{8}\pi \]

    C)  \[\frac{7\,}{3}\pi \]                   

    D)       \[\frac{8\,\pi }{3}\]

    Correct Answer: D

    Solution :

    [d] \[v=\omega \sqrt{{{A}^{2}}-{{x}^{2}}}\]
    \[a={{\omega }^{2}}x\]
    \[v=a\]                          (according to question
    \[\left| velocity \right|\text{ = }\left| acceleration \right|\text{ })\]
    \[~\omega \sqrt{{{A}^{2}}-{{x}^{2}}}\,=\,{{\omega }^{2}}x\]
    \[~\sqrt{{{A}^{2}}-{{x}^{2}}}\,=\,\omega x\]
    \[{{A}^{2}}-{{x}^{2}}={{\omega }^{2}}{{x}^{2}}\]
    \[25-16={{\omega }^{2}}\times 16\]
    \[9={{\omega }^{2}}\times 16\]
    \[\omega \,\,=\,\,\sqrt{\frac{9}{16}}\,\,=\,\frac{3}{4}\]
    \[T\,\,=\,\,\frac{2\pi }{\omega }\,=\,\frac{2\pi }{3}\,\times 4\,\,=\,\,\frac{8\,\pi }{3}\,\sec \]


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