1. The problem statement, all variables and given/known data Basically, a particle is moving in a straight line in a bubble chamber. Then, it splits into two other particles. The new particles start to rotate, but while one rotates clockwise, the other rotates counter-clokwise. The trajectory of the particles before and after the split can be viewed in the attached diagram. The question simply asks why the particles rotate in opposing directions. http://img24.imageshack.us/img24/5083/spiralt.jpg [Broken] 2. Relevant equations No calculations are required. 3. The attempt at a solution I thought this question was fairly simple, with the answer being conservation of angular momentum. The initial particle moves in a straight line, so it has no angular momentum. If the new particles are rotating, their angular momentum must have the same magnitude but opposing orientation, so that the system's angular momentum remains zero. Problem solved, right? Except the correct answer given is that "the particles have opposite charges". Huh? Did the question ignore angular momentum as a possible explanation or am I simply way off?