An electron accelerates from rest through an electric field and into a magnetic field

as shown in the diagram below. The plates have a potential difference of $105V$ and

the magnetic field has a magnitude of $0\mathrm{.}75T.($Remember: $m_e=9\mathrm{.}1{10}^{-31}kg$ and $e$

$=1\mathrm{.}6{10}^{-19}C.)$

$($a$)$ Calculate the initial speed of the electron upon entering the magnetic field.

$($b$)$ Calculate the magnitude and direction of the magnetic force on the electron.

$($c$)$ Calculate the radius of the electron's circular path.