9th Class Science Work and energy Question Bank Work, Energy and Power

  • question_answer
    A bullet of mass 10 gm moving with velocity of 100 m/sec hits a wooden log and penetrates it upto thickness of 5 cm. The resistance force of the log is

    A)  \[200N\]

    B)  \[500N\]

    C)  \[1000N\]  

    D)  \[600N\]

    Correct Answer: C

    Solution :

     According to work energy theorem, loss in kinetic energy \[=F\times S\] Since, finally the bullet stops, the loss in kinetic energy \[=F\times S\] Since, finally the bullet stops, therefore loss in kinetic energy = initial kinetic energy. or            \[\frac{1}{2}m{{v}^{2}}=F\times S\] or            \[\frac{1}{2}\times 10\times {{10}^{-3}}\times 100=F\times 5\times {{10}^{-2}}\] or            \[F=1000\,\,N\]


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