I am an undergraduate physics student and found myself thinking about a scenario where two positively charged projectiles are fired at an angle to the horizontal at a velocity with a certain separation. So they will be subject to a gravitational force and perpendicular to this, an electrostatic force. The distance dependent acceleration is something I have not covered before and am unsure as to how to calculate where the projectiles will land. Lets give the projectiles a mass of 1kg and a charge of +1mC. Say they are fired at 45degrees to the horizontal with a velocity of 40m/s. They are fired in the same direction at the same time but separated by 1m. If we say this happens on a co-ordinate system, we can say they are fired from +/- 0.5 x, and parallel to the y axis. I have worked out that the time of flight is 5.77s and that the y co-ordinates of the impact points are +/- 160.2m. How can I set up the calculus to solve for x?