Imagine for a moment a closed system. All that exists in this system is two like-charged bodies which would have the tendency to repel each other. These bodies of mass are connected by a short string. Say this string is cut or suddenly snaps, and the bodies begin to fly apart. This means the tension energy in the string is changed into kinetic energy, and no energy is created or destroyed. According to Relativity, however, an increase in velocity creates an increase in mass. This means the total mass of the system is increased, which is potential energy. Is this not in violation in the Law of Conservation? I assume I am missing some factor or just dont fully understand the theory, so maybe a more knowledgeable person can solve this parodox or point out some aspect of relativity I failed to consider.