JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        A particle projected vertically upwards attains a maximum height H. If the ratio of the times to attain a height\[h(h<H)\]is\[\frac{1}{3}\]then,

    A)  \[4h=3H\]          

    B)  \[3h=4H\]

    C)  \[3h=H\]                            

    D)  \[4h=H\]

    Correct Answer: A

    Solution :

                    From the equation of motion \[{{v}^{2}}={{u}^{2}}+2as\] \[{{v}^{2}}-{{u}^{2}}=2as\] \[{{0}^{2}}-{{u}^{2}}=2\times (-g)\times H\] \[u=\sqrt{2gH}\] Now,        \[h=ut-\frac{1}{2}g{{t}^{2}}\]                 \[h=(\sqrt{2gH})t-\frac{1}{2}g{{t}^{2}}\] This equation is quadratic in t. Solve for t we get, values for time. Ratio is \[\frac{{{t}_{1}}}{{{t}_{2}}}=\frac{1}{3}\] (given) substituting values, we get \[4h=3H\]


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