1. The problem statement, all variables and given/known data In a velocity selector E and B fields are perpendicular. Which of the following conditions on the direction of the particle's velocity can result in no net force assuming the E and B are nonzero? 2. Relevant equations F = Eq + q(vxB) 3. The attempt at a solution The answer is B. A) v is parallel to E --Not sure why this wouldn't work. Since E is perpendicular to B why can't it result in F = 0? F = E + vB B) v is parallel to (ExB) --If I recall my cross product information correctly. v will be perpendicular to both E and B therefore I get F = E + vB. What's the difference between the two?