Electric Force - example
From Coulomb’s Law, we know that there is an electric force between any two charges:
F = kq1q2/r122 , with the direction determined by the signs of the charges.
F = (9x109 Nt-m2/C2) * (3 C) * (5 C) / (.07 m)2 = 2.76 x 1013 Nt. Note that we ignore the sign on any charge when calculating the magnitude.
Since the charges are opposite, the force is attractive!