An object $A$ of mass $20 \mathrm{kg}$ and travelling at $20 \mathrm{m} {\mathrm{s}}^{-1}$ crashes into another object $B$ of mass $200 \mathrm{kg}$ and travelling at $10 \mathrm{m} {\mathrm{s}}^{-1},$ in the same direction. After the collision, object $A$ bounces back in opposite direction at a speed of $10 \mathrm{m} {\mathrm{s}}^{-1}$. The speed of the object $B$ after the collision is

• Correct answer
  A

  $13 \mathrm{m} {\mathrm{s}}^{-1}$
• B

  $12 \mathrm{m} {\mathrm{s}}^{-1}$
• C

  $14 \mathrm{m} {\mathrm{s}}^{-1}$
• D

  $20 \mathrm{m} {\mathrm{s}}^{-1}$

Hence, the correct answer is option: 'A'.