1. The problem statement, all variables and given/known data 2. The attempt at a solution 3. Relevant equations In the first problems of that book i was using the Galilean transformations where V1 = V2 + V But if i use that then V1 = 0.945 - 0.6 V1 = 0.345 Is not the same result, so im confused. In this new problems we are using Lorentz transformations. When i should use Galilean transformations and when to use Lorentz transformations?