v, E and B are Mutually Perpendicular #8211; In this situation, if E and B are such that as shown in figure, then the particle will pass through the field with same velocity. F = F<sub>e</sub> + F<sub>m</sub> = 0 i.e. a = (F/m) = 0 And in this situation, as /F<sub>e</sub>/ = /F<sub>m</sub>/ i.e. qE = qvB ⇒ v = E/B