JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति JEE PYQ - Work Energy Power and Collision

  • question_answer
    A particle is moving in a circular path of radius a under the action of an attractive potential \[\text{U=-}\frac{\text{k}}{\text{2}{{\text{r}}^{\text{2}}}}\]. Its total energy is : [JEE Main Online 08-04-2018]

    A) Zero     

    B) \[\text{-}\frac{\text{k}}{\text{4 }{{\text{a}}^{\text{2}}}}\]

    C) \[\frac{k}{2{{a}^{2}}}\]

    D)

    Correct Answer: A

    Solution :

    [a] \[U=\frac{-k}{2{{r}^{2}}}\Rightarrow F=\frac{-du}{dr}=\frac{k}{{{r}^{3}}}\]
    This force is providing centripetal acceleration.
    \[\frac{m{{v}^{2}}}{a}=\frac{k}{{{a}^{3}}}\]            \[(\because r=a)\]
    \[\Rightarrow m{{v}^{2}}=k/{{a}^{2}}\]
    \[\Rightarrow \frac{1}{2}m{{v}^{2}}=\frac{k}{2{{a}^{2}}}\]
    \[\Rightarrow T.E.=\frac{-k}{2{{a}^{2}}}+\frac{k}{2{{a}^{2}}}=0\]
    \[\text{-}\frac{\text{3}}{\text{2}}\frac{\text{k}}{{{\text{a}}^{\text{2}}}}\]


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