1. The problem statement, all variables and given/known data A particle of mass M and charge Q>0 moves in a region of space where the magnetic field has a constant magnitude B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with a speed v? (a) QvB toward the east (b) zero (c) QvB toward the west (d) QvB upward (e) QvB toward the south 2. Relevant equations F= qv x B 3. The attempt at a solution My understanding of the question is that the magnetic field and the velocity are parallel and in the opposite direction, so shouldn't the magnetic field be zero?