Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2007

  • question_answer
    The velocity v (in cm/s) of a particle is given in terms of time t (in sec) by the relation \[y=at+\frac{b}{t+c};\] the dimensions of a, b and c are

    A) \[a\,\text{=}\,\text{ }\!\![\!\!\text{ }{{\text{L}}^{\text{2}}}\text{ }\!\!]\!\!\text{ ,}\,\text{b}\,\text{=}\,\text{ }\!\![\!\!\text{ T }\!\!]\!\!\text{ ,}\,\text{c}\,\text{=}\,\text{ }\!\![\!\!\text{ L}{{\text{T}}^{\text{2}}}\text{ }\!\!]\!\!\text{ }\]

    B)  \[a\,\text{=}\,\text{ }\!\![\!\!\text{ L}{{\text{T}}^{\text{2}}}\text{ }\!\!]\!\!\text{ ,}\,\text{b}\,\text{=}\,\text{ }\!\![\!\!\text{ LT }\!\!]\!\!\text{ ,}\,\text{c}\,\text{=}\,\text{ }\!\![\!\!\text{ L }\!\!]\!\!\text{ }\]

    C) \[a\,\text{=}\,\text{ }\!\![\!\!\text{ L}{{\text{T}}^{\text{-2}}}\text{ }\!\!]\!\!\text{ ,}\,\text{b}\,\text{=}\,\text{ }\!\![\!\!\text{ L }\!\!]\!\!\text{ ,}\,\text{c}\,\text{=}\,\text{ }\!\![\!\!\text{ T }\!\!]\!\!\text{ }\]

    D) \[a\,\text{=}\,\text{ }\!\![\!\!\text{ L }\!\!]\!\!\text{ ,}\,\text{b}\,\text{=}\,\text{ }\!\![\!\!\text{ LT }\!\!]\!\!\text{ ,}\,\text{c}\,\text{=}\,\text{ }\!\![\!\!\text{ }{{\text{T}}^{2}}\text{ }\!\!]\!\!\text{ }\]

    Correct Answer: C

    Solution :

    \[v=at+\frac{b}{t+c}\] From principle of homogeneity of dimensions, Dimensions of at = dim of v \[\therefore \]                  Dimensions of a = dim of  \[\frac{v}{t}\]                                                 \[=\frac{[L{{T}^{-1}}]}{[T]}=[L{{T}^{-2}}]\] Dimensions of c = dim of \[t=[T]\] Dimensions of \[\frac{b}{t}=\] dim of v Dimensions of b = dim of vt                 \[=[L{{T}^{-1}}]\times [T]=[L]\]


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