Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    When a uniform solid sphere and a disc of the same mass and of the same radius roll down an inclined smooth plane from rest to the same distance, then the ratio of the times taken by them is

    A)  15 : 14                                 

    B)  \[{{15}^{2}}:{{14}^{2}}\]

    C)  \[\sqrt{14} :\sqrt{15}\]                            

    D)  14:15

    Correct Answer: C

    Solution :

                    \[t=\frac{1}{\sin \theta }\sqrt{\frac{2h}{g}\left( 1+\frac{{{K}^{2}}}{{{R}^{2}}} \right)}\] \[\Rightarrow \]               \[\frac{{{t}_{S}}}{{{t}_{D}}}=\sqrt{\frac{1+{{\left( \frac{{{K}^{2}}}{{{R}^{2}}} \right)}_{S}}}{1+{{\left( \frac{{{K}^{2}}}{{{R}^{2}}} \right)}_{D}}}}\]                 \[=\sqrt{\frac{1+\frac{2}{5}}{1+\frac{1}{2}}}=\sqrt{\frac{14}{15}}\]


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