A projectile is fired upward, so its vertical velocity will Slow down, stop, speed up.
Speed up, stop, speed up.
Slow down, stop, slow down

Slow down, stop, speed up.

It slows due to gravity (acting against gravity due to upward motion), stops because at maximum height vertical velocity is zero and the body has only the horizontal velocity, speed up due to action of gravity on the body due to downward motion.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach