JEE Main & Advanced Sample Paper JEE Main Sample Paper-45

  • question_answer
    A point performs simple harmonic oscillation of period T and the equation of motion is given by \[x=a\,\sin \,\left( \omega t+\frac{\pi }{6} \right)\].After the elapse of what fraction of the time period, the velocity of the point will be equal to half of its maximum velocity?

    A)  \[\frac{T}{8}\]                                  

    B)  \[\frac{T}{6}\]

    C)  \[\frac{T}{3}\]                                  

    D)  \[\frac{T}{12}\]

    Correct Answer: D

    Solution :

     Writing the given equation of a point performing SHM \[x=a\,\,\sin \,\,\left( \omega t+\frac{\pi }{6} \right)\]             ?(i) Differentiating Eq. (i), w.r.t. time, we obtain \[v=\frac{dx}{dt}=a\omega \,\,\cos \,\,\left( \omega t+\frac{\pi }{6} \right)\] It is given that \[v=\frac{2\omega }{2},\] so that \[\frac{a\omega }{2}=a\omega \,\,\cos \,\,\left( \omega t+\frac{g}{6} \right)\] or         \[\frac{1}{2}=\cos \,\left( \omega t+\frac{\pi }{6} \right)\] or         \[\cos \,\frac{\pi }{3}\,=\cos \,\left( \omega t+\frac{\pi }{6} \right)\] or         \[\frac{\pi }{3}=\omega t+\frac{\pi }{6}\,\,\Rightarrow \,\,\omega t\,=\frac{\pi }{6}\] or         \[t=\frac{\pi }{6\omega }=\frac{\pi \times T}{6\times 2\pi }=\frac{T}{12}\] Thus, at \[\frac{T}{12}\] velocity of the point will be equal to half of its maximum velocity.


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