J & K CET Engineering J and K - CET Engineering Solved Paper-2011

  • question_answer
    Two balls are projected from the same point    in directions inclined at \[{{45}^{o}}\] and \[{{60}^{o}}\] to the horizontal respectively. If they attain the same height, the ratio of their velocities of projection is equal to

    A)  \[\sqrt{3}:1\]        

    B)  \[3:1\]

    C)  \[3:2\]         

    D)  \[3:2\]

    Correct Answer: D

    Solution :

    Let the velocity of two balls at the projection time is \[{{u}_{1}}\] and \[{{u}_{2}}\] and H be the corresponding height attained by both balls. Height of first ball = Highest of second ball \[\frac{u_{1}^{2}\,\,{{\sin }^{2}}\,{{45}^{o}}}{2g}=\frac{u_{2}^{2}\,\,{{\sin }^{2}}\,\,{{60}^{o}}}{2g}\] \[\Rightarrow \] \[u_{1}^{2}\times 1/2=u_{2}^{2}\times 3/4\] \[\Rightarrow \] \[{{u}_{1}}:{{u}_{2}}=\sqrt{3}:\sqrt{2}\]


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