J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    A body id falling freely under gravity starting from a point O.it passes through two points A and B. If \[OA=\,2AB,\] then the ratio of time takes by the body to cover the distance OA and AB is

    A)  \[2\,\pm \,\sqrt{6}\]

    B)  \[\sqrt{2}\]

    C)  \[2+\sqrt{2}\]

    D)  \[2+\sqrt{6}\]

    Correct Answer: B

    Solution :

    Let  \[AB=x\] \[\therefore \] \[OA=2x\] and time taken by the body to cover the distance OA and AB  are \[{{t}_{1}}\] and \[{{t}_{2}}\] respectively. Then, \[2x=0+\frac{1}{2}gt_{1}^{2}\] \[[\because \,\,u=0]\] \[\Rightarrow \] \[4x=gt_{1}^{2}\] and \[x=0+\frac{1}{2}gt_{2}^{2}\] \[\Rightarrow \] \[2x=gt_{2}^{2}\] \[\therefore \]  Required ratio \[=\frac{{{t}_{1}}}{{{t}_{2}}}=\frac{\sqrt{\begin{matrix}    4x  \\    g  \\ \end{matrix}}}{\sqrt{\begin{matrix}    2x  \\    g  \\ \end{matrix}}}\] \[\Rightarrow \] \[\frac{{{t}_{1}}}{{{t}_{2}}}=\frac{\sqrt{2}}{1}\]


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