Two identical balls, each possessing a charge of 2.00 × 10^ -7 C...

The electric force between two point charges is given by Coulomb's law:

$F = \dfrac{1}{4\pi\epsilon_0} \dfrac{q_1 q_2}{r^2}$

Given that the charges on the balls are $q_1 = q_2 = 2.00 \times 10^{-7} \text{ C}$ and the initial separation is $r = 5.0 \text{ cm} = 5.0 \times 10^{-2} \text{ m}$.

Substituting the given values into the formula:

$F = \dfrac{(9 \times 10^9) \times (2.00 \times 10^{-7})^2}{(5.0 \times 10^{-2})^2}$

$F = \dfrac{9 \times 10^9 \times 4.00 \times 10^{-14}}{25 \times 10^{-4}}$

$F = \dfrac{36 \times 10^{-5}}{25 \times 10^{-4}}$

$F = 1.44 \times 10^{-1} \text{ N} = 0.144 \text{ N}$

The mass of the balls and the length of the strings do not affect the magnitude of the electric force at the instant of release.