J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    Rectilinear motion is performed in accordance with the formulae \[s=\frac{2}{9}\sin \frac{\pi t}{2}+{{s}_{0}}.\] Then the acceleration at the end of the 1st second (in\[cm/{{s}^{2}}\]) is

    A)  \[\frac{{{\pi }^{2}}}{18}\]            

    B)  \[\frac{{{\pi }^{2}}}{7}\]

    C)  \[\frac{-{{\pi }^{2}}}{9}\]

    D)  \[\frac{-{{\pi }^{2}}}{18}\]

    Correct Answer: D

    Solution :

    Given,   \[s=\frac{2}{9}\sin \,\frac{\pi t}{2}+{{s}_{0}}\] \[\Rightarrow \] \[\frac{ds}{dt}=\frac{2}{9}\cos \frac{\pi t}{2}\times \frac{\pi }{2}\] \[\Rightarrow \] \[a=\frac{{{d}^{2}}s}{d{{t}^{2}}}=-\frac{{{\pi }^{2}}}{18}\sin \frac{\pi t}{2}\] At \[t=1s,\] \[a=-\frac{{{\pi }^{2}}}{18}cm/{{s}^{2}}\]


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