An Electron Moves in a Region Where the Magnetic Field

Multiple Choice

An electron moves in a region where the magnetic field is uniform, has a magnitude of 60 μT, and points in the positive x direction. At t = 0 the electron has a velocity that has an x component of 30 km/s, a y component of 40 km/s, and a z component of zero. What is the pitch of the resulting helical path?

A) 13 mm
B) 32 mm
C) 24 mm
D) 18 mm
E) 3.8 mm