The particles are released from rest simultaneously. They repel one another, and start moving apart. After a long time, when the particles are far apart, essentially all of the initial electric potential energy has been converted into kinetic energy, some taken away by particle 1 and the rest by particle 2. What percent of the initial energy does particle 2 end up carrying away

Since you have not included the experiment situation and the data, of course, i can not give you specific details about it. but i can you with this question.1) i will assume that the motion is projectile (parabolic) motion.2) yes, the horizontal distance depends on the horizontal velocity as, naming vx the horizontal velocity and t the time, it is: x = vx × t3) now, observe that the flight time depends on the vertical velocity as, naming voy the initial vertical velocity, t the time and y the vertical distance before reaching the ground: y = yo + voy×t - gt² / 2.the higher the initial vertical velocity (voy) the longer the object will be flying and so t will be higher in the equation for the horizontal distance.that explains the relationship between the horizontal distance and the horizontal velocity.

C. it comes from the core of the earth.