Punjab Medical Punjab - MET Solved Paper-2008

  • question_answer
    If force\[(F)\], work \[(W)\] and velocity \[(V)\] are taken as fundamental quantities, then the dimensional formula of time\[(T)\]is

    A) \[[WFv]\]                           

    B) \[[WF{{v}^{-1}}]\]

    C) \[[{{W}^{-1}}{{F}^{-1}}v]\]          

    D) \[[W{{F}^{-1}}{{v}^{-1}}]\]

    Correct Answer: D

    Solution :

    Let\[T\propto {{F}^{a}}{{W}^{b}}{{v}^{c}}\]                                         ... (i) \[[T]={{[ML{{T}^{-2}}]}^{a}}{{[M{{L}^{2}}{{T}^{-2}}]}^{b}}{{[L{{T}^{-1}}]}^{c}}\] \[[{{T}^{1}}]=[{{M}^{a+b}}][{{L}^{a+2b+c}}][{{T}^{-2a-2b-c}}]\] Comparing the powers, we get                 \[a+b=0\]                                            ... (ii)                 \[a+2b+c=0\]                                     ... (iii)                 \[-2a-2b-c=1\]                                   ... (iv) Solving Eqs. (ii), (iii) and (iv), we get                 \[a=-1,\,\,b=-1,\,\,c=-1\] Therefore, from Eq. (i),                 \[[T]=k[{{F}^{-1}}{{W}^{1}}{{v}^{-1}}]\] Taking\[k=1\]in SI system, we have                 \[[T]=[W{{F}^{-1}}{{v}^{-1}}]\]


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