9th Class Science Time and Motion Question Bank Motion

  • question_answer
    If two bodies of different masses \[{{m}_{1}}\] and \[{{m}_{2}}\] are dropped from different heights \[{{h}_{1}}\] and \[{{h}_{2}}\], then ratio of the times taken by the two to drop through these distances is

    A)  \[{{h}_{1}}:{{h}_{2}}\]                                  

    B)  \[{{h}_{2}}/{{h}_{1}}\]

    C)  \[{{\sqrt{h}}_{1}}:\sqrt{{{h}_{2}}}\]         

    D)         \[{{h}^{2}}_{1}:{{h}^{2}}_{2}\]

    Correct Answer: C

    Solution :

     Distance fallen by a freely body, \[\Rightarrow \]   \[s=\frac{1}{2}g{{t}^{2}}\]             \[s\propto {{t}^{2}}\]               ? [\[\because \frac{1}{2}g\]is constant] \[\therefore \]      \[\frac{{{s}_{1}}}{{{s}_{2}}}=\frac{t_{1}^{2}}{t_{2}^{2}}\] \[\Rightarrow \]   \[\frac{{{h}_{1}}}{{{h}_{2}}}=\frac{t_{1}^{2}}{t_{2}^{2}}\] \[\Rightarrow \]   \[\frac{{{t}_{1}}}{{{t}_{2}}}=\sqrt{\frac{{{h}_{1}}}{{{h}_{2}}}}\]


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