Question

the electron beam in a television tube consist of electron accelerated from rest through a potential difference of about 20000 v. what is the speed of the electrons?( ignore relativistic effects.) electron rest mass is 9.11x 10^31kg and electronic charge is 1.6x10^19c

Answer 1

$E=\frac{mv^2}2,$

$\varphi=\frac Ee,$

$\varphi=\frac{mv^2}{2e},$

$v=\sqrt{\frac{2e\varphi}{m}},$

$v=84\cdot 10^6~\frac ms.$