1. The problem statement, all variables and given/known data 2. Relevant equations - 3. The attempt at a solution When the positive particle enters the electric field it will turn and move toward the negative plate. So a) the displacement vector will change direction until it's directed toward the negative plate, parallel with the electric field. b) the velocity will also change direction in the same way as the displacement. c) the linear momentum is directed in the same way as the velocity d) the acceleration will be directed inwards from the curve movement, so it will be parallel at first but not in the end. So the answer would be that a), b) and c) are parallel (not at first, but in the end) and d) is parallel at first but not in the end. Is my reasoning incorrect?