Question

What must be the distance in meters between point charge q1 = 30.3 µC and point charge q2 = -68.2 µC for the electrostatic force between them to have a magnitude of 7.09 N?

Answer 1

Answer: 1.62 m

Explanation: In order to solve this problem we have to use the definition of Coulomb force whic is given by:

F=(k*q1*q2)/d^2  where k is a constant 9*10^9 N/C^2*m^2. d is the distance between tha charges q1 and q2.

then we can:

d^2= (k*q1*q2)/F= (9*10^9*30.3*10^-6*68.2*10^-6)/7.09=1.62 m

(note we have  considered q2 as positive because we are determining d^2 by using the magnitude of the electric Force bewteen the charges).