Explanation:
Given that,
Mass of the raindrops, [tex]m=0.5\ g=0.0005\ kg[/tex]
Charges, [tex]q=1\ mC=10^{-3}\ C[/tex]
Distance between raindrops, d = 1 cm = 0.01 m
(a) The force due to motion of raindrop is balanced by the electric force between charges. It is given by :
[tex]ma=\dfrac{kq^2}{r^2}[/tex]
a is the acceleration of the raindrop
[tex]a=\dfrac{kq^2}{r^2m}[/tex]
[tex]a=\dfrac{9\times 10^9\times (10^{-3})^2}{(0.01)^2\times 0.0005}[/tex]
[tex]a=1.8\times 10^{11}\ m/s^2[/tex]
(b) It is clear that the acceleration is too large. It can break apart the rain drop.
(c) If the charge is of the factor of [tex]10^{-8}\ C[/tex], the charge would be more reasonable.
Hence, this is the required solution.