An Electron Moving Perpendicular to a Uniform Magnetic Field Of 3.2

Multiple Choice

An electron moving perpendicular to a uniform magnetic field of $3.2 \times 10 ^ { - 2 } \mathrm {~T}$ moves in a circle of radius $0.40 \mathrm {~cm}$ . How fast is this electron moving? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } , m _ { \text {electron } } = 9.11 \times 10 ^ { - 31 } \mathrm {~kg} \right)$

A) $0.80 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$
B) $3.0 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$
C) $2.2 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$
D) $1.9 \times 10 ^ { 6 } \mathrm {~m} / \mathrm { s }$
E) $1.9 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$