JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    The potential energy of a particle varies with height \[h\] from a fixed point as \[E=\left( \frac{\operatorname{P}\sqrt{h}}{h+Q} \right)\] where, \[P\] and \[Q\] are constants. The dimensions of \[PQ\] are

    A) \[[M{{L}^{2}}{{T}^{-2}}]\]                            

    B) \[[{{M}^{3/2}}{{L}^{3/2}}{{T}^{-2}}]\]

    C) \[[M{{L}^{7/2}}{{T}^{-2}}]\]                        

    D)  \[[M{{L}^{3/2}}{{T}^{-2}}]\]

    Correct Answer: C

    Solution :

    Given\[,E=\frac{P\sqrt{h}}{h+Q}\]                                           ... (i) Dimension of \[E=\] Dimension of potential energy                 \[=[M{{L}^{2}}{{T}^{-2}}]\] From Eq. (i), we get Dimension of \[Q=\] Dimension of\[h=[{{M}^{0}}L{{T}^{0}}]\] \[\therefore \]Dimension of\[P\] \[=\frac{Dimension\,\,of\,\,E\times Dimension\,\,of\,\,(h+O)}{Dimension\,\,of\,\,\sqrt{h}}\]                 \[=\frac{[M{{L}^{2}}{{T}^{-2}}][{{M}^{0}}L{{T}^{0}}]}{[{{M}^{0}}{{L}^{1/2}}{{T}^{0}}]}=[M{{L}^{5/2}}{{T}^{-2}}]\] Hence, dimensions of\[PQ\]                 \[=[M{{L}^{5/2}}{{T}^{-2}}][{{M}^{0}}L{{T}^{0}}]=[M{{L}^{7/2}}{{T}^{-2}}]\]


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