JEE Main & Advanced Physics Mathematical Tools, Units & Dimensions Question Bank Self Evaluation Test - Physical World, Units and Measurements

  • question_answer
    If velocity (V), force (F) and energy (E) are taken as fundamental units, then dimensional formula for mass will be

    A) \[{{V}^{-2}}{{F}^{0}}{{E}^{3}}\]

    B)  \[{{V}^{0}}F{{E}^{2}}\]

    C)  \[V{{F}^{-2}}{{E}^{0}}\]

    D)  \[{{V}^{-2}}{{F}^{0}}E\]

    Correct Answer: D

    Solution :

    [d] \[Let\,(M)\,={{V}^{a}}{{F}^{b}}{{E}^{c}}\] Putting the dimensions of V, F and E, we have \[(M)={{(L{{T}^{-1}})}^{a}}\times {{(ML{{T}^{-2}})}^{b}}\times {{(M{{L}^{2}}{{T}^{-2}})}^{c}}\] \[or\,{{M}^{1}}={{M}^{b+c}}{{L}^{a+b+2c}}{{T}^{-a-2b-2c}}\] Equating the powers of dimensions, we have \[b+c=1\] \[a+b+2c=0;\text{ }-a-2b-2c=0\] which give a \[=-2,\text{ }b=0\text{ }and\text{ }c=1.\] Therefore\[(M)=({{V}^{-2}}{{F}^{0}}E)\]


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