A velocity selector has a magnetic field that has a magnitude equal to 0.28 T and is perpendicular to an electric field that has a magnitude equal to 0.46 MV/m. What must the speed of a particle be for that particle to pass through the velocity selector undeflected? What kinetic energy must electrons have in order to pass through the velocity selector undeflected?

Assume, for these electrons, their motion is from left to right through the velocity selector and the electric field is upward. This means the electric force is downward and hence then the magnetic force must be upward and the magnetic field into the page. We can apply the condition for transnational equilibrium to relate v to E and B. Then use the definition of kinetic energy to find the energies of the electrons that pass through the velocity selector undeflected.
https://www.britannica.com/science/Lorentz-force