일반물리학 2 — Magnetic Fields: Problem 3

3 A particular type of fundamental particle decays by transforming into an electron \( e^- \) and a positron \( e^+ \). Suppose the decaying particle is at rest in a uniform magnetic field \( \vec{B} \) of magnitude \( 9.57 \text{ mT} \) and the \( e^- \) and \( e^+ \) move away from the decay point in paths lying in a plane perpendicular to \( \vec{B} \). How long after the decay do the \( e^- \) and \( e^+ \) collide?