A ring of radius R has charge Q distributed uniformly on it. At a distance x ($\ne$ 0) from centre on its axis.(consider axial points only)

If x = 0, for a charge - q and mass m, escape velocity is $\sqrt{\frac{\mathrm{qQ}}{2{\mathrm{\pi \epsilon }}_0\mathrm{mR}}}$

Potential cannot be greater than $\frac{\mathrm{Q}}{4{\mathrm{\pi \epsilon }}_0\mathrm{R}}$

Electric field cannot be greater than $\frac{\mathrm{Q}}{6\sqrt{3}{\mathrm{\pi \epsilon }}_0{\mathrm{R}}^2}$

For small value of x, a charge - q of mass m released, oscillates with time period of $2\mathrm{\pi }\sqrt{\frac{4{\mathrm{\pi \epsilon }}_0{\mathrm{mR}}^3}{\mathrm{qQ}}}$