Question - Two protons, seperated by a large distance, are fired directly at each other. The closest approach in this head-on collision is 3.0 x 10^14 m. One proton starts with two times the speed of the other. Assuming there is no delection from the original path, determine the initial speed of each proton. Solution - I read through my notes and text book but I couldnt find any way to connect speed with this question. Is there any specific equations to use?