1. The problem statement, all variables and given/known data A mass spectograph is used to identify some element and 12/6 Carbon is used as a reference. 12C has a circular path of radius = 5cm. The particle of the unknown element is travelling at the same velocity as the 12C. What is the mass of one atom of the unknown element if the unknown element has a circular path radius of 10cm? (The figures may be off because I made up this question basing on other questions to improve my understanding of mass/charge ratio) 2. Relevant equations Centripetal force = mv^2/r Elect. F = Bvq Mass/charge ratio 3. The attempt at a solution Firstly I made centripetal force equal Elct. F: mv^2/r = Bvq Using algebra: Bvqr = mv^2 Bqr/v = mv B/v = m/qr The mass/charge ratio of 12C = 12/6 = 2 As the two things are travelling at same velocity in same magnetic field (B), m/qr = m/qr 2/0.05 = m/qr 40 = m/qr 40 x 0.08 = m/q 3.2 = m/q This is where I am stuck. I don't fully understand the relationship between m and q and other things that may be involved! I cannot really see a way around this - and this is precisely why I made this question up. I don't understand the basics but can do generic questions because I've practised solving general questions... Please help!