A Charge in a Uniform Field

In a uniform field a charge feels a constant force $F = qe$, so it has a constant acceleration:

$$a = \frac{qE}{m}$$

along E for a positive charge, against E for a negative one.

For an electron or a proton the weight is tiny next to the electric force and is left out. A heavier charged drop can hang still when $qe = mg$.

A charge entering sideways keeps its speed across the field and speeds up along it: it moves on a parabola.