일반물리학 2 — Magnetic Fields: Problem 42

42 A particle of mass 12 g and charge 80 \(\mu\)C moves through a uniform magnetic field, in a region where the free-fall acceleration is \(\vec{g} = -9.8\hat{j}\) m/s\(^2\). The velocity of the particle is a constant \(\vec{v} = 20\hat{i}\) km/s, which is perpendicular to the magnetic field. What, then, is the magnetic field?