JEE Main 2019 — Mechanical Properties of Solids Question with Solution

A boy’s catapult is made of rubber cord which is $42 \mathrm{c}\mathrm{m}$ long, with $6 \mathrm{m}\mathrm{m}$ diameter of cross-section and of negligible mass. The boy keeps a stone weighing $0.02 \mathrm{k}\mathrm{g}$ on it and stretches the cord by $20 \mathrm{c}\mathrm{m}$ by applying a constant force. When released, the stone flies off with a velocity of $20 \mathrm{m}{\mathrm{s}}^{-1}$ . Neglect the change in the area of cross-section of the cord while stretched. The Young’s modulus of rubber is closest to: