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Punjab Medical Punjab - MET Solved Paper-2008

  • question_answer
    A ball of mass \[0.6kg\] attached to a light inextensible string rotates in a vertical circle of radius \[0.75m\] such that it has a speed of\[5m{{s}^{-1}}\] when the string is horizontal. Tension in string when it is horizontal on other side is\[(g=10m{{s}^{-2}})\]

    A) \[30N\]                                

    B) \[26N\]

    C) \[20N\]                                

    D) \[6N\]

    Correct Answer: C

    Solution :

    Tension in the string when it makes angle \[\theta \] with the vertical,                 \[T=\frac{m{{v}^{2}}}{r}+mg\cos \theta \] When the string is horizontal,\[\theta ={{90}^{o}}\] Here,\[m=0.6\,\,kg,\,\,r=0.75\,\,m,\,\,v=5m/s\] Hence,  \[T=\frac{m{{v}^{2}}}{r}+mg\times 0=\frac{m{{v}^{2}}}{r}\] \[\therefore \]  \[T=\frac{0.6\times {{(5)}^{2}}}{0.75}=20\,\,N\]


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