A mass $\text{m}$ moves in a circle on a smooth horizontal plane with velocity ${\mathrm{v}}_0$ at a radius ${\mathrm{R}}_0$ . The mass is attached to a string which passes through a smooth hole in plane as shown.

The tension in the string is increased gradually and finally $\text{m}$ moves in a circle of radius $\frac{{\mathrm{R}}_0}{2}$. The final value of the kinetic energy is:

• A

  $\mathrm{m}{\mathrm{v}}_0^2$
• B

  $\frac{1}{4}\mathrm{m}{\mathrm{v}}_0^2$
• Correct answer
  C

  $2\mathrm{ }\mathrm{m}{\mathrm{v}}_0^2$
• D

  $\frac{1}{2}\mathrm{m}{\mathrm{v}}_0^2$

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