In this problem, i and j refer to unit vectors in the X and Y directions respectively. A small particle whose mass is 10-12 kg and carrying a net charge of +5 μC enters a region of space where the magnetic field is 2T i. The velocity of the particle at some instant of time is 0.03C i + 0.04Cj (where C = speed of light).
If the magnetic field were to be directed perpendicular to the particle instead of in the X direction as given, what would be the radius of the particle's resulting circular motion?