Two small plastic spheres are given positive electrical charges. when they are 15 cm apart, the repulsive force between them has magnitude of 0.220n. if the two charges are equal in magnitude, what is the charge on each sphere?

The repulsive forces between two point charges is given by the following rule:
F = (k x q1 x q2) / (r^2) where:
q1 and q2 are the charges
k is coulomb's constant = 9 x 10^9 N. m2/ C2
r is the distance between the two charges.

Assume that q1=q2=q
Applying in the above equation, we find that:
0.22 = (9 x 10^9 x q^2) / (0.15^2)
0.22 = 4 x 10^11 q^2
q^2 = 5.5 x 10^-13
q = 7.4 x 10^-7 C

Therefore, the value of each of the two charges is 7.4 x 10^-7 C