RAJASTHAN PMT Rajasthan - PMT Solved Paper-2007

  • question_answer
    Two stones are projected with the same speed but making different angles with the horizontal. Their horizontal ranges are equal. The angle of projection of one is \[\frac{\pi }{3}\]and the maximum height reached by it is 102 m. Then the maximum height reached by the other in metre is

    A)  336                                       

    B)  224

    C)  56                         

    D)         34

    Correct Answer: D

    Solution :

    We know that if two stones have same horizontal range, then this implies that both are projected at\[\theta \]and\[{{90}^{o}}-\theta \]. Here,     \[\theta =\frac{\pi }{3}={{60}^{o}}\]                 \[{{90}^{o}}-\theta ={{90}^{o}}-{{60}^{o}}={{30}^{o}}\] For first stone, Max. height\[=102=\frac{{{u}^{2}}{{\sin }^{2}}{{30}^{o}}}{2g}\] For second stone, Max. height,\[h=\frac{{{u}^{2}}{{\sin }^{2}}{{30}^{o}}}{2g}\] \[\therefore \]  \[\frac{h}{102}=\frac{{{\sin }^{2}}{{30}^{o}}}{{{\sin }^{2}}{{60}^{o}}}=\frac{{{(1/2)}^{2}}}{{{(\sqrt{3}/2)}^{2}}}\] or            \[h=102\times \frac{1/4}{3/4}=34\,\,m\]


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