A proton is accelerated from rest through a voage of 9.0kV. It then enters a region of space where
there is a uniform electric field and a uniform magnetic field that are at right angles to each other, as illustrated in the figure.
Suppose that the electric field has a value of 4.5x105N/C. What magnetic field is needed so that the protons will not bend? (We will use classical mechanics for the relationship between energy and velocity.)