Answer:
the magnitude of the second charge is 0.000156 C.
Step-by-step explanation:
Given;
mangitude of the first charge, q₁ = 0.0005 C
attractive force between the two charges, F = 7.0 N
distance between the two charges, r = 10 m
let the magnitude of the second charge = q₂
The magnitude of the second charge is calculated by applying Coulomb's law;

Where;
K is Coulomb's constant = 9 x 10⁹ Nm²/C²

Therefore, the magnitude of the second charge is 0.000156 C.