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JEE Main & Advanced Sample Paper JEE Main Sample Paper-24

  • question_answer
    Consider an elliptically shaped rail PQ in the vertical plane with \[OP=3\] m and \[OQ=4\]m. A block of mass 1 kg is pulled along the rail from P to Q with a force of 18 N, which is always parallel to line PQ (see figure). Assuming no frictional losses, the kinetic energy of the block when it reaches Q is \[(n\times 10)\,J\]. The value of n is: (Take acceleration due to gravity \[=10\,\,m{{s}^{-2}}\])

    A)  50 J                            

    B)  100J

    C)  \[5\times {{10}^{2}}\] J                      

    D)  200 J

    Correct Answer: A

    Solution :

    From work energy theorem Work done by all forces = Change in kinetic energy \[{{W}_{F}}+{{W}_{mg}}\,={{K}_{f}}\,-{{K}_{i}}\] \[18\times 5+(1\times 10)\,(-4)\,={{K}_{f}}\] \[90-40\,={{K}_{f}}\,\Rightarrow \,{{K}_{f}}=50\,J\]


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