You have two electrons held at a fixed distance X from each other. You measure the opposing force is Y. Now you bring the electrons closer to each other, and then let them go so they can fly apart. As the electrons move apart and reach distance X, will the opposing force still be Y, or will it be less/more than that? Similarly, if you reserves it so you had the particles approaching each other (let's say electron & positron pair), what would happen with the force between them at distance X? Put simply, does the speed towards or away from each other effect force?