BCECE Engineering BCECE Engineering Solved Paper-2004

  • question_answer
    A stone thrown at an angle \[\theta \] to the horizontal reaches a maximum height H. Then the time of flight of stone will be:

    A) \[\sqrt{\frac{2H}{g}}\]                  

    B)        \[2\sqrt{\frac{2H}{g}}\]

    C)        \[\frac{2\sqrt{2H\sin \theta }}{g}\]                         

    D)        \[\frac{\sqrt{2H\sin \theta }}{g}\]

    Correct Answer: B

    Solution :

    Maximum height reached by the stone. \[H=\frac{{{u}^{2}}{{\sin }^{2}}\theta }{2g}\]                       ?(i) where \[u\] is the velocity with which stone is thrown at angle\[\theta .\] Time of flight,    \[T=\frac{2u\sin \theta }{g}\]                     ?(ii)  Using Eq. (i) \[{{u}^{2}}=\frac{2gH}{{{\sin }^{2}}\theta }\] \[\Rightarrow \]                               \[u=\frac{\sqrt{2gH}}{\sin \theta }\] Substituting the value of \[u\]in Eq. (ii), we obtain \[T=\frac{2}{g}\frac{\sqrt{2gH}}{\sin \theta }\times \sin \theta \] \[=\frac{2}{g}\times \sqrt{2gH}\] \[=2\sqrt{\frac{2H}{g}}\]


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