Problem 3.390

Non-relativistic protons move rectilinearly in the region of space where there are uniform mutually perpendicular electric and magnetic fields with \(E=4.0 \mathrm{kV} / \mathrm{m}\) and \(B=50 \mathrm{mT} .\) The trajectory of the protons lies in the plane \(x z\) (Fig. 3.102 ) and forms an angle \(\varphi=30^{\circ}\) with the \(x\) axis. Find the pitch of the helical trajectory along which the protons will move after the electric field is switched off.