1. The problem statement, all variables and given/known data a proton moves with a velocity <6*105,3*105> m/s through a magnetic field given by <.2,.2> T a. Find the magnetic force per unit charge on the proton b. Find the work done by this force 2. Relevant equations Fm=qv x B 3. The attempt at a solution For part a, I used a property of the cross product to simply divide the force by the charge Fm/q=v x B So by finding the cross product, I believe that I reached the force per unit charge which gives (3/5)*105 N/C For part b, I know that the charge is moving with constant velocity (no net force). Therefore the work done by the magnetic force must be negative. (some outside force must do work against it?) I have no idea how I would go about finding the "work done by this force", I almost feel as if there's not enough information provided. Wouldn't I at least need the time period over which to consider? Thank you.