47.tAn electron travels at 2✖107 m/s in a plane perpendicular to a uniform 0.01 T magnetic field. What is the radius of the travel path? (electron mass = 9.1✖10-31 kg, charge on electron = 1.6✖10-19 Coul)
(A)t5.2 cm
(B) 3.8 cm
(C) 2.1 cm
(D) 1.1 cm
(E) 0.5 cm
答案：D
統計：A:0,B:0,C:0,D:1,E:0
難度：計算中