There is a uniform spherically symmetric surface charge density at a distance R_0 from the origin. The charge distribution is initially at rest and…

There is a uniform spherically symmetric surface charge density at a distance $\displaystyle \mathrm{R}_0$ from the origin. The charge distribution is initially at rest and starts expanding because of mutual repulsion. The figure that represents best the speed V(R(t)) of the distribution as a function of its instantaneous radius $\displaystyle \mathrm{R}(\mathrm{t})$ is :