Example
An electron is to be fired in a magnetic field of strength 6 gauss directed into the screen so that it hits a target located at: x = +25 cm; y = + 42 cm.
The distance to the target is: d = SQR[x2 + y2] = 48.88 cm. If we choose the minimum circle method, r = d/2 = 24.44 cm = .2444 m.
From r = mv/qB, v = qBr/m = (1.6 x 10-19 C) * (6 x 10-4 T) * (.2444 m) / (9.1 x 10-31 kg) =