If the particle in Problem 30 is an electron instead of a proton, what is the radius of the trajectory? 

Data  From Problem 30

A proton has an initial velocity v S B when it enters a region in which B_A(vector) proton has an initial velocity is parallel to the z direction (Fig. P20.28). (a) Show that the proton will move in a circle that lies in the x–y plane. (b) If v_B = 500 m/s and B = 0.80 T,