KVPY Sample Paper KVPY Stream-SX Model Paper-10

  • question_answer
    A homogeneous circular plate of radius r has a circular hole as shown below.
    Coordinates of centre of mass of plate with respect to given origin is

    A) \[(0,0)\]             

    B) \[\left( -\frac{r}{2},0 \right)\]

    C) \[\left( -\frac{r}{6},0 \right)\]                   

    D) \[\left( -\frac{r}{6},\frac{r}{6} \right)\]

    Correct Answer: C

    Solution :

    The x-coordinate of complete disc
    Is \[{{X}_{CM}}=\frac{{{m}_{1}}{{x}_{1}}+{{m}_{2}}{{x}_{2}}}{{{m}_{1}}+{{m}_{2}}}\]
    Treating removed mass \[{{m}_{2}}\]as negative mass, we have
    \[0=\frac{\frac{3}{4}m\cdot {{x}_{0}}+\frac{m}{4}\cdot \frac{r}{2}}{\frac{3}{4}m+\frac{m}{4}}\]\[\Rightarrow \]\[{{x}_{0}}=\frac{-r}{6}\]


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