1. The problem statement, all variables and given/known data http://postimg.org/image/gdfsdglpt/ v=2.2E5 m/s l=0.16 m I=5.3 A N=820 mp=1.67E-27 kg B=3.4E-2 T Looking for radius of curvature in the solenoid with the above variables. 2. Relevant equations BIl=F 3. The attempt at a solution BIl=mv^2/r 3.4E-2*5.3*0.16=1.67E-27*(2.2E5)^2/r r=2.8E-15 m The correct answer however, is 6.8E-2 m, so what did I do wrong?