A bullet of mass $10\, g$ moving horizontally with a velocity of $400\, m s^{-1}$ strikes a wood block of mass $2\, kg$ which is suspended by light inextensible string of length $5\, m.$ As a result, the centre of gravity of the block found to rise a vertical distance of $10\, cm.$ The speed of the bullet after it emerges out horizontally from the block will be ................... $\mathrm{ms}^{-1}$

  • [NEET 2016]
  • A

    $160$

  • B

    $120$

  • C

    $100$

  • D

    $80$

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