# Newtons Laws-Force with respect to time

1. Oct 15, 2008

### mikee

1. The problem statement, all variables and given/known data An electron is oriented between two charged plates (oriented vertically). The electron experiences a constant force perpendicular to the plates. It has a mass of 9.0 x 10^-31 kg, is moving vertically with a velocity of 2.0 x 10^6m/s and enters the region between the two plates. The region has a height of 1cm and while in it the electron experiences a force of 3.0 x 10^-18N. How long does the electron stay in the region, and what is the horizontal component of velocity as soon as the electron passes through the region

2. Relevant equations

3. The attempt at a solutionOk heres how i started it, i figured out the acceleration of the particle by F= ma , a= 3.0 x 10^-18/9.0 x 10^-31 and therefore now that i have the acceleration and the x which = 0.001m i can use those to figure out the time and the velocity, so i figured out the velocity by using the equation Vo^2 + 2(a)(d)= V^2
and i used 2.6 x 10^6 for Vo^2 and solved for V and once i found that i used V to solve for the time and i used V= a(t) + Vo is this method correct or am i totally off, would i have to incorporate gravity into it, and also since it says the force is perpendicular to the plates would i have to take the force in the x direction instead of the y direction like i did and if so is it going left or right, those are some details i just wasnt to sure on, if anyone could help thanks alot

2. Oct 15, 2008

### nasu

The electron is moving upward initially (let's call this y direction).
The acceleration is horizontal (x direction).
1 cm is the height of the plates. There is no acceleration along this direction.
The motion has two components:
- uniform motion along y, with given speed
- accelerated motion along x, with zero initial velocity