[SOLVED] Momentum and Lorentz-force 1. The problem statement, all variables and given/known data Hi all. I have two questions. 1) Please take a look at page 22 in this document (look at the bottom): http://walet.phy.umist.ac.uk/P615/Notes.pdf It says that the momentum in GeV/c for a particle which moves in a magnetic field is given by: p = 0.3*B*r, where B is in Teslas and r is the radius in metres. I can derive p = qBr, but how does it become p = 0.3Br when p is measured in GeV/c? 2) If I have a proton moving in a magnetic field, where the magnetic field is perpendicular to the velocity-vector of the proton and the proton turns right, does the magnetic field point into or out of the plane? 3. The attempt at a solution 1) Ok, I know that the net-force is mv^2/r = q(E + v x B) = qvB, so p = q*B*r. But this is in m/s. How do I convert to GeV/c to obtain the expression above? 2) I tried using the right-hand-rule: The index finger in the direction of the velocity, the thumb in the direction of F (right, since it is turning this way) and then the middle-finger points upwards, which is the direction of B? Can you confirm this? Thanks in advance. Sincerely Niles.