Question

A positive point charge of magnitude q and mass m is dropped from a great
height h onto another similar charge fixed on the ground. The minimum distance
between the charges in CGS units is:

Answer 1

 in CGS units the condition of the stop will be

$$mg(h - l) = q^{2}(\frac{1}{l} - \frac{1}{h}),$$

then

$$l = \frac{q^{2}}{mgh}$$