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JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    Time period of a block suspended from the upper plate of a parallel plate capacitor by a spring of stiffness \[K\] is \[T\], when block is uncharged. If a charge \[q\] is given to the block then, die new time period of oscillation will be

    A) \[T\]                                     

    B) \[>T\]

    C)  \[<T\]                                  

    D)  \[\ge T\]

    Correct Answer: A

    Solution :

    The forces that act on the block are \[qE\] and\[mg\]. Since, \[qE\] and \[mg\] are constant forces, the only variable elastic force changes by\[kx\]  (where, \[x\] is the elongation in the spring). Unbalanced (restoring) force,\[F=-kx\] \[\Rightarrow \]               \[-m{{\omega }^{2}}x=-kx\] \[\Rightarrow \]               \[\omega =\sqrt{\frac{k}{m}}=T\]


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