Question

A freei pitch ball of mass 6 gram carries a positive charge of (1/3 )* 10 ^{​​​​​​-7} coulomb what must be nature and magnitude of charge that should be given to second pitch ball fixed 5 cm vertically below the former baseball so that the upper bonus stationery.

Answer 1

Mass of the pith ball, m = 6 g = .006 kg

Charge on it is, q = 1/3 × 10-7 C

Let Q be the charge on the other pith ball placed at 5 cm or 0.05 m below.

The weight of the upper pith ball is balanced by the electrostatic repulsion between the balls.

mg = kqQ/r2

=> (0.006)(9.8) = (9 × 10^9)( 1/3 × 10-7)Q/(0.05^2)

=> Q = 0.0049 c