15. An electron of mass, m, initially moving horizontally to the right at speed v enters a region of uniform magnetic field, B, pointed [DOWN] at right angles to the plane in which the electron is moving. In order to determine the radius of the electron's path in the uniform magnetic field, provide a system diagram [1A], the concept(s) involved [1A], the steps required [2A], the equations to be used [1A] and a sketch of the proton's path in the magnetic field [1A]. Do not try to solve.