1. The problem statement, all variables and given/known data A stable uncharged particle is break into 2 parts of mass m, one of which is charged -2Q. The two parts then go in the direction perpendicular to a uniform magnetic field B. After what time will the particles collide? 2. Relevant equations 3. The attempt at a solution I suppose the time to be the period of one revolution of each particle, which leads to the result ∏m / BQ. Is that correct?