Problem 3.389

A non-relativistic proton beam passes without deviation through the region of space where there are uniform transverse $\mathrm{mu}-$ tually perpendicular electric and magnetic fields with $E=120 \mathrm{kV} / \mathrm{m}$ and $B=50 \mathrm{mT}$. Then the beam strikes a grounded target. Find the force with which the beam acts on the target if the beam current is equal to $I=0.80 \mathrm{~mA}$