An electron moves in a circular path with a speed of $1\mathrm{.}34{10}^7\frac{m}{s}$ in the presence of a uniform magnetic field with a magnitude of $2\mathrm{.}14$ mT $.$ The electron's path is perpendicular to the field.

$($a$)$ What is the radius $($in cm $)$ of the circular path?

$cm$

$($b$)$ How long $($in s$)$ does it take the electron to complete one revolution?

Consider the result for the radius, and how it depends on speed. How is speed in uniform circular motion related to period? s