A positive point charge is released from rest at a distance ${\mathrm{r}}_0$ from a positive line charge with uniform charge density. The speed $\left(\mathrm{v}\right)$ of the point charge, as a function of instantaneous distance $\mathrm{r}$ from line charge, is proportional to

• A

  $\mathrm{v}\propto \left(\frac{\mathrm{r}}{{\mathrm{r}}_0}\right)$
• Correct answer
  B

  $\mathrm{v}\propto \sqrt{\ln \left(\frac{\mathrm{r}}{{\mathrm{r}}_0}\right)}$
• C

  $\mathrm{v}\propto \ln \left(\frac{\mathrm{r}}{{\mathrm{r}}_0}\right)$
• D

  $\mathrm{v}\propto {\mathrm{e}}^{\raisebox{1ex}{$+\mathrm{r}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{r}}_0$}\right.}$

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