A bullet made of lead moving with velocity v, hits a wall. Its 50 % kinetic energy is converted into heat, then increase in temperature will be : (s$\to$specific heat, J $\to$ mechanical equivalent of heat)

• A

  $\frac{2{\mathrm{v}}^2}{\mathrm{JS}}$

• B

  $\frac{{\mathrm{v}}^2}{4\mathrm{JS}}$

• C

  $\frac{{\mathrm{v}}^2\mathrm{S}}{\mathrm{J}}$

• D

  $\frac{{\mathrm{v}}^2.\mathrm{s}}{2\mathrm{J}}$