1. The problem statement, all variables and given/known data A particle of mass m(naught) moves throught the lab at .6c. Suddenly it explodes into two fragments. Fragment 1 has mass .66m(naught) and moves at .8c in the same direction as the original particle had been moving. Determine the velocity (magnitude and direction) and mass of fragment 2? 2. Relevant equations m = m(naught) / sqrt (1-(v^2/c^2) p = m(naught) v(naught) / sqrt (1-(v^2/c^2) 3. The attempt at a solution I have worked this problem for the last 3 hours. I am not sure how to find the mass of the 2nd particle and also everytime I work the problem I get a nonsense answer. I understand that momentum is conserved and initial energy = final energy. I was trying to use p total = p piece 1 + p piece 2 where p is the relativistic momentum. The m(naught) is throwing me off also. Thansks for any help.