Two particles , each of mass `m` and carrying charge `Q` , are separated by some distance. If they are in equilibrium under mutual gravitational and electrostatic force then `Q//m (in C//kg)` is of the order of

Options

A. `10^(-5)`
B. `10^(-10)`
C. `10^(-15)`
D. `10^(-20)`

Answer

B

Explanation

The attractive gravitational force `= G(m^(2))/(r^(2))` and the repulsive electrostatic force `= k(Q^(2))/(r^(2))`.
where r is the separation between two particles
For equilibrium, `(Gm^(2))/(r^(2)) = (kQ^(2))/(r^(2))`
or `(Q)/(m) = sqrt((G)/(k)) = [(6.67 xx 10^(-11))/(9 xx 10^(9))]^(1//2) ~ 10^(-10)`