I'm stuck on this question and I'm not sure where to start. A positively charged ion (m = 3.34 x 10^-26 kg) was accelerated from rest through a potential difference of 1.66 x 10^4 V. This ion now enters a region where there is a magnetic field (B = 3.20 x 10^-2 T) that is perpendicular to the direction of its motion. If the magnetic force on the ion is 5.78 x 10^-15 N, what is the charge on the ion? I've done this question many times, and it seems that there's on unknown I have to find first (I think the speed), but I can't get it for some reason. I also tried equating formulas....that worked, but I got the wrong answer afterwards.