An electron of mass 9.11 x 10-31 (9.11e-31) kg travels in a circular orbit within a large evacuated chamber. The orbit has a 2.0 mm radius and is perpendicular to a B-field of 0.030 T. What's the electron's speed? For this problem, the only equation i can think to apply is F=qvB. I know B, i know q, i need to solve for V, but how do i get F? F =ma, but that still leaves me stuck because i dont know the acceleration of the electron... I understand this problem and know what to do, i'm just missing something somewhere because i don't seem to have enough to solve the problem, although i know its in there. I'm just not seeing it, and need a slight prod in the right direction.