Here’s How to Crack It
Since the velocity of particle Y is parallel to the direction of B, particle Y feels no
magnetic force (the angle θ between vY and B is 0, and sin 0 = 0). Since the
velocity of particle Z is antiparallel to the direction of B, particle Z also feels no
magnetic force (the angle θ between vZ and B is 180°, and sin 180° is also 0).
However, the velocity of particle X is perpendicular to the direction of B (that is,
θ= 90°), so the magnetic force on particle X is qvB sin θ= qvB sin 90° = qvB.
Therefore, particle X feels the greatest magnetic force.