JEE Main & Advanced Sample Paper JEE Main - Mock Test - 4

  • question_answer
    A stone projected with a velocity u at an angle \[\theta \] with the horizontal reaches maximum height \[{{H}_{1}}\]. When it is projected with velocity u at an angle \[\left( \frac{\pi }{2}-\theta  \right)\] with the horizontal, it reaches maximum height \[{{H}_{2}}\]. The relation between the horizontal range R of the projectile, heights \[{{H}_{1}}\] and \[{{H}_{2}}\] is

    A) \[R=4\,\sqrt{{{H}_{1}}{{H}_{2}}}\]

    B) \[R=4\,({{H}_{1}}-{{H}_{2}})\]

    C) \[R=4\,({{H}_{1}}+{{H}_{2}})\]

    D) \[R=\frac{H_{1}^{2}}{H_{2}^{2}}\]

    Correct Answer: A

    Solution :

    \[{{H}_{1}}=\frac{{{u}^{2}}{{\sin }^{2}}\theta }{2g}\] and \[{{H}_{2}}=\frac{{{u}^{2}}{{\sin }^{2}}(90{}^\circ -\theta )}{2g}=\frac{{{u}^{2}}{{\cos }^{2}}\theta }{2g}\]
    \[{{H}_{1}}{{H}_{2}}=\frac{{{u}^{2}}{{\sin }^{2}}\theta }{2g}\times \frac{{{u}^{2}}{{\cos }^{2}}\theta }{2g}=\frac{{{({{u}^{2}}\sin 2\theta )}^{2}}}{16{{g}^{2}}}=\frac{{{R}^{2}}}{16}\]
    \[\therefore \,\,\,R=4\sqrt{{{H}_{1}}{{H}_{2}}}\]


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