BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    A spring is held compressed so that its stored energy is 2.4 J. its ends are in contact with masses 1 g and 48 g placed on a functionless table. When the spring is released, the heavier mass wilt acquire a speed of

    A) \[\frac{2.4}{49}m{{s}^{-1}}\]      

    B)        \[\frac{2.4\times 48}{49}m{{s}^{-1}}\]

    C) \[\frac{{{10}^{3}}}{7}cm{{s}^{-1}}\]         

    D)        \[\frac{{{10}^{6}}}{7}cm{{s}^{-1}}\]

    Correct Answer: C

    Solution :

    \[\frac{1}{2}{{m}_{1}}v_{1}^{2}+\frac{1}{2}{{m}_{2}}v_{2}^{2}=2.4\] or \[{{m}_{1}}v_{1}^{2}+{{m}_{2}}v_{2}^{2}=4.8\]                            ?(i) Now,     \[{{m}_{1}}{{v}_{1}}={{m}_{2}}{{v}_{2}}\] or \[{{v}_{1}}=48\,{{v}_{2}}\] Using Eq. (i) \[\frac{1}{1000}{{(48{{v}_{2}})}^{2}}+\frac{48}{1000}v_{2}^{2}=4.8\] or            \[\frac{48}{1000}(49v_{2}^{2})=4.8\] \[\therefore \]  \[{{v}_{2}}=\frac{10}{7}m/s=\frac{{{10}^{3}}}{7}cm/s\]


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