# Proton, electron and coordinates

• 21385

## Homework Statement

A proton sits at coordinates (x,y) = (0,0), and an electron at (d,h), where d>>h. At time t=0, a uniform electric field E of unknown magnitude but pointing in the positive y direction is turned on. Assuming that d is large enough that the proton-electron interaction is negligible, the y coordinates of the two particles will be equal (at equal time)

b)at an undetermined value since E is unknown;
d)nowhere: they move in opposite directions

E=F/q
F=ma

## The Attempt at a Solution

The correct answer is a) but I don't know why. I have no idea how the answer connects d, a x-coordinate, with the final y-coordinate.

This is my attempt::

E=F/q
Since the E is the same and the q is the same, the 2 Forces must be the same
(mass of electron)(acceleration of electron)=(mass of proton)(acceleration of the proton)
(acceleration of electron)=1833(acceleration of proton)

S=(0.5)(acceleration of electron)t^2+(0.5)(acceleration of proton)t^2
of course, S=h-0 or S=h, and (acceleration of electron)=1833(acceleration of proton)
h=(0.5)(1833a(proton))t^2+(0.5)(a(proton))t^2
a(proton)=h/(917t^2)