Circular Motion of Charges: a Proton Starting from Rest Travels

Multiple Choice

Circular motion of charges: A proton starting from rest travels through a potential of 1.0 kV and then moves into a uniform 0.040-T magnetic field. What is the radius of the proton's resulting orbit? (m_proton = 1.67 × 10^-27 kg, e = 1.60 × 10^-19C)

A) 0.080 m
B) 0.11 m
C) 0.14 m
D) 0.17 m