1. The problem statement, all variables and given/known data A nucleus at rest undergoes spontaneous radioactive decayby emitting an electron of momentum 1.73 MeV/c and at right angle to to the direction of electron, a neutrino of momentum 1 MeV/c.Find the direction and momentum of the recoiling nucleus. Here c is the velocity of light. 2. Relevant equations 3. The attempt at a solution I CAN do this...but I am wondering if we are to employ the relativistic momentum concept... Can anyone clarify?