F = k*q1*q2/r², r = √(k*q1*q2/F) = √(9*10^(9)*4*10^(-9)*10*10^(-9)/9*10^(-3) =
= 10^(-3)*√40 = 0.0063 м
F = k*q1*q2/r², r = √(k*q1*q2/F) = √(9*10^(9)*4*10^(-9)*10*10^(-9)/9*10^(-3) =
= 10^(-3)*√40 = 0.0063 м