One end of a light spring of natural length $\mathrm{d}$ and spring constant $\mathrm{k}$ is fixed on a rigid wall and the other is fixed to a smooth ring of mass $\mathrm{m}$ which can slide without friction in a vertical rod fixed at a distance d from the wall. Initially, the spring makes an angle of $37°$ with the horizontal as shown in the diagram. When the system is released from rest, find the speed of the ring when the spring becomes horizontal. $(\sin 37° = 3/5)$

• Correct answer
  A

  $\text{d}\sqrt{\frac{\text{3g}}{\text{2d}}+\frac{\text{k}}{\text{16m}}}$
• B

  $\text{d}\sqrt{\frac{\text{2g}}{\text{3d}}-\frac{\text{k}}{\text{21m}}}$
• C

  $\text{d}\sqrt{-\frac{\text{4g}}{\text{2d}}+\frac{\text{k}}{\text{12m}}}$
• D

  $\text{d}\sqrt{-\frac{\text{8g}}{\text{4d}}+\frac{\text{k}}{\text{28m}}}$

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