AMU Medical AMU Solved Paper-1998

  • question_answer
    A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration\[{{a}_{c}}\]is varying with time \[t\] as\[{{a}_{c}}={{k}^{4}}r{{t}^{2}}\]where k is constant. The power delivered to the particle by the forces acting on it is

    A)  \[m{{k}^{2}}{{r}^{2}}{{t}^{2}}\]

    B)  \[m{{k}^{2}}{{r}^{2}}t\]

    C)  \[\pi m{{k}^{2}}{{r}^{2}}{{t}^{2}}\]         

    D)  \[m{{k}^{4}}{{r}^{2}}t\]

    Correct Answer: D

    Solution :

    : Acceleration \[{{a}_{c}}={{k}^{4}}r{{t}^{2}}\] centripetal acceleration \[=\frac{{{v}^{2}}}{r}\] \[\therefore \]\[\frac{{{v}^{2}}}{r}={{k}^{4}}r{{t}^{2}}\] or\[{{v}^{2}}={{k}^{4}}{{r}^{2}}{{t}^{2}}\] From Work - Energy theorem, \[W=\frac{1}{2}m{{v}^{2}}\] \[\therefore \]\[W=\frac{1}{2}m\times {{k}^{4}}{{r}^{2}}{{t}^{2}}\] \[\therefore \]\[\frac{dW}{dt}=\frac{2m{{k}^{4}}{{r}^{2}}t}{2}\] Power \[=m{{k}^{4}}{{r}^{2}}t\].


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