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JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
                              In the figure, the ball \[P\] is released from rest, when the spring is at its natural length. For the block \[Q\] of mass \[2{{m}_{0}}\] to leave contact with ground at some stage, the minimum mass of P must be

    A) \[{{m}_{0}}\]                                     

    B) \[2{{m}_{0}}\]

    C) \[{{m}_{0}}/2\]                

    D)  \[{{m}_{0}}/4\]

    Correct Answer: A

    Solution :

    The block will experience maximum upward force, when the ball \[P\] is at its lowest position\[(x)\]. Energy conservation gives                 \[mgx=\frac{1}{2}k{{x}^{2}}or\,\,x=2mg/k\]        ... (i) For the block \[Q\] to leave contact                 \[kx=2{{m}_{0}}g\]                                          ... (ii) Solving Eqs. (i) and (ii), we get                 \[m=2{{m}_{0}}/2={{m}_{0}}\]


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