Two particles each have a mass of 7.1 x 10-4 kg. One has a charge of +6.7 x 10-6 C, and the other has a charge of -6.7 x 10-6 C. They are initially held at rest at a distance of 0.88 m apart. Both are then released and accelerate toward each other. How fast is each particle moving when the separation between them is one-half its initial value?