Here's a practice diploma question I found on the internet, this isn't homework. I'm studying, I just need help on how to do this type of question. http://www.paulway.com/physics30/p30dips/p30jan2002.pdf [Broken] (Page 11 Numerical Response #5) Answer: 4.80x10^-3 1. The problem statement, all variables and given/known data In the magnetic field mass spectrometer shown, the radius of curvature of a proton’s path is 3.00 m. What is the magnetic field intensity? 2. Relevant equations I'm guessing this one, but I don't see how radius would be added to solve it. [PLAIN]http://k.min.us/idLl6m.png [Broken] 3. The attempt at a solution I couldn't even attempt this one, sorry, I tried, but maybe I have the wrong equation? I've posted other questions, but as I was reviewing I understand that I never really knew how to do this kind of problem. So for anyone to help me starting with the basics, would be helpful as any help at all is highly appreciated.