JEE Main & Advanced Sample Paper JEE Main - Mock Test - 42

  • question_answer
    A particle executes simple harmonic motion with a time period of\[16\,s\]. At time \[t=2s,\]the particle crosses the mean position while at \[t=4s,\]its velocity is \[4\,m/{{s}^{-1}}.\]. The amplitude of motion in metre is

    A) \[\sqrt{2}\pi \]

    B)                    \[16\sqrt{2}\pi \]

    C) \[24\sqrt{2}\pi \]

    D)        \[\frac{32\sqrt{2}}{\pi }\]

    Correct Answer: D

    Solution :

    At \[t=2\text{ }sec,\]the particle crosses mean position. At \[t=4\text{ }sec,\]its velocity is \[4\,m{{s}^{-1}}\] For simple harmonic motion, \[y=a\,\sin \,\omega t\] \[\therefore \,\,y=a\,\sin \left( \frac{2\pi }{T} \right)t\] \[{{y}_{1}}=a\,\sin \left[ \left( \frac{2\pi }{16} \right)\times 2 \right]=a\sin \left( \frac{\pi }{4} \right)=\frac{a}{\sqrt{2}}\]        ?.(i) After 4 sec or after 2 sec from mean position, \[{{y}_{1}}=\frac{a}{\sqrt{2}},\] velocity \[=4\text{ }m{{s}^{-1}}\] \[\therefore \] Velocity \[=\omega \sqrt{{{a}^{2}}-y_{1}^{2}}\] \[\Rightarrow \,\,4=\left( \frac{2\pi }{16} \right)\sqrt{{{a}^{2}}-\frac{{{a}^{2}}}{2}}\]                from (i)] \[\Rightarrow \,\,4=\frac{\pi }{8}\times \frac{a}{\sqrt{2}}\] or \[a=\frac{32\sqrt{2}}{\pi }\]metre.


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