1. The problem statement, all variables and given/known data 2. Relevant equations [itex]KE = 1/2mv^2[/itex] [itex]F_B=I(L x B)[/itex] 3. The attempt at a solution I have the answer to this, (D) but I don't know how to get it. I know that the gained kinetic energy is equal to the lost potential energy of the system. What's the potential energy of the system? ILB? If so, how does that translate to answer D?