JEE Main & Advanced Sample Paper JEE Main - Mock Test - 20

  • question_answer
    A force F acting on a body depends on its displacement S as \[F\propto {{S}^{-1/3}}\]. The power delivered by F will depend on displacement as

    A) \[{{S}^{2/3}}\]                       

    B) \[{{S}^{1/2}}\]

    C) \[{{S}^{0}}\]              

    D) \[{{S}^{-5/3}}\]

    Correct Answer: C

    Solution :

    [c] : As\[F\propto {{S}^{-1/3}},\] \[\therefore \]Acceleration,\[a\propto {{S}^{-1/3}}\] \[a=\frac{dv}{dt}=\frac{dv}{dS}.\frac{dS}{dt}=\frac{dv}{dS}v\]i.e.,\[v\frac{dv}{dS}\propto {{S}^{-1/3}}\] Integrating both sides, we get \[{{v}^{2}}\propto {{S}^{2/3}}\]or\[v\propto {{S}^{1/3}}\] As\[P=Fv\] \[\therefore \]\[P\propto {{S}^{-1/3}}{{S}^{1/3}}\]or\[P\propto {{S}^{0}}\]. i.e., power is independent of S.


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