Example $21-15$: Electron accelerated by electric field. E An electron $($mass m $=9\mathrm{.}11$ x $10-31$ kg$)$ is accelerated in the uniform field $($E $=2\mathrm{.}0$ x $104$ N$/$C$)$ between two parallel charged plates. The separation of the plates is $1\mathrm{.}5$ cm$.$ The electron is accelerated from rest near the negative plate and passes through a tiny hole in the positive plate. $($a$)$ With what speed does it leave the hole? $($b$)$ Show that the gravitational force can be ignored. Assume the hole is so small that it does not affect the uniform field between the plates.