Solution to task 345 from Chertov´s for extramural stud

Solution to task 345 from Chertov´s for extramural stud

345. An electron, having passed a path from one plate to another in a flat capacitor, acquired a velocity v = 105 m / s. The distance between the plates is d = 8 mm. Find: 1) the potential difference U between the plates; 2) surface charge density σ on the plates.