Here, charge on pitch ball Mass of pith ball

The weight of the pitch ball acts vertically downwards.

Let be charge on the pith ball held above the pitch ball , so that the pith ball remains stationary.
It can be possible only, if the charges on two pith balls are of opposite signs,

i.e. If charge on pith ball is positive, charge on must be negative. Then, the force on pith ball due to , i.e., will act vertically upwards (figure).

For charge to remain stationary,

Here,

or

──────────────────────────────────────────────────────────────────────────────────────────