NEET Physics Mathematical Tools, Units & Dimensions Question Bank Dimensions

  • question_answer
    If velocity \[v\], acceleration \[A\] and force \[F\] are chosen as fundamental quantities, then the dimensional formula of angular momentum  in terms of \[v,\,A\] and \[F\] would be

    A)             \[F{{A}^{-1}}v\]     

    B)             \[F{{v}^{3}}{{A}^{-2}}\]

    C) \[F{{v}^{2}}{{A}^{-1}}\]

    D) \[{{F}^{2}}{{v}^{2}}{{A}^{-1}}\]

    Correct Answer: B

    Solution :

        \[L\propto {{v}^{x}}{{A}^{y}}{{F}^{z}}\] \[\Rightarrow \] \[L=k{{v}^{x}}{{A}^{y}}{{F}^{z}}\] Putting the dimensions in the above relation \[[M{{L}^{2}}{{T}^{-1}}]=k{{[L{{T}^{-1}}]}^{x}}{{[L{{T}^{-2}}]}^{y}}{{[ML{{T}^{-2}}]}^{z}}\] Þ \[[M{{L}^{2}}{{T}^{-1}}]=k[{{M}^{z}}{{L}^{x+y+z}}{{T}^{-x-2y-2z}}]\] Comparing the powers of \[M,\,L\] and \[T\] \[z=1\]             ?(i) \[x+y+z=2\]               ?(ii) \[-x-2y-2z=-1\]            ?(iii) On solving (i), (ii) and (iii) \[x=3,\,y=-2,\,z=1\] So dimension of \[L\] in terms of \[v,\,A\] and \[f\] \[[L]=[F{{v}^{3}}{{A}^{-2}}]\]


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