A boy’s catapult is made of rubber cord which is $42\, cm$ long, with $6\, mm$ diameter of cross -section and of negligible mass. The boy keeps a stone weighing $0.02\, kg$ on it and stretches the cord by $20\, cm$ by applying a constant force. When released, the stone flies off with a velocity of $20\, ms^{-1}$. Neglect the change in the area of cross section of the cord while stretched. The Young’s modulus of rubber is closest to
  • A$10^3\, Nm^{-2}$
  • B$10^6\, Nm^{-2}$
  • C$10^8\, Nm^{-2}$
  • D$10^4\, Nm^{-2}$
JEE MAIN 2019, Medium
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