JEE Main & Advanced JEE Main Online Paper (Held On 08 April 2018)

  • 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)  \[\text{-}\frac{\text{3}}{\text{2}}\frac{\text{k}}{{{\text{a}}^{\text{2}}}}\]

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

    D)  \[\frac{k}{2{{a}^{2}}}\]

    Correct Answer: A

    Solution :

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


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