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JCECE Engineering JCECE Engineering Solved Paper-2011

  • question_answer
    A ball rolls of the top of a stair way with a horizontal velocity\[u\,\,m{{s}^{-1}}\]. If the steps are \[h\] metre high and \[b\] metre wide, the ball will hit the edge of the nth step, where \[n\] is

    A) \[\frac{2hu}{g{{b}^{2}}}\]                                            

    B) \[\frac{2h{{u}^{2}}}{g{{b}^{2}}}\]

    C) \[\frac{2h{{u}^{2}}}{gb}\]                            

    D)  \[\frac{h{{u}^{2}}}{g{{b}^{2}}}\]

    Correct Answer: B

    Solution :

    Let the ball strike the, nth step after r second. Vertical distance travelled by ball\[=nh=\frac{1}{2}g{{t}^{2}}\]. Horizontal distance travelled by ball\[=nb=ut\] or            \[t=\frac{nb}{u}\]                 \[nh=\frac{1}{2}g{{\left( \frac{nb}{u} \right)}^{2}}\] or            \[n=\frac{2{{u}^{2}}}{g}\frac{h}{{{b}^{2}}}\]


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