A stone tied to a string is rotated with a uniform speed in a vertical plane. If mass of the stone is m, length of the string is r and linear speed of the stone is v, then tension in the string when the stone is at its lower point is ( g = acceleration due to gravity)

• A

  mg

• B

  ${\mathrm{mv}}^2/\mathrm{r}$

• C

  $\left({\mathrm{mv}}^2/\mathrm{r}\right)−\mathrm{mg}$

• D

  $\left({\mathrm{mv}}^2/\mathrm{r}\right)+\mathrm{mg}$