please explain in detail, thank you so much

8. A particle of mass 5.00 g and a charge of 5.00 /C is held at point A, while a second particle of mass 8.00 g and a charge of 8.00 /C is held at point B. When released, the two particles fly apart, and a detector indicates a speed of 208 m/s for the lighter particle when the separation between the particles becomes 10.0 cm. Determine the a. speed of the heavier particle when the separation is 10.0 cm. b. distance between points A and B. 9. A charge of 5.0 /C is fixed at the origin and a particle of mass 2.7 g and charge 3.0 /C is initially located at x = 1.0 m. The particle is shot with an initial velocity of 20 m/s directly toward the fixed charge. How far does the particle travel before it stops and bounces back? 5.0 uC 20 m/s 3.0 /C - = = = = 1.0 m