# Homework Help: Electric Field & Capacitor Problem HELP

1. Jul 5, 2007

### isufuaks

Electric Field & Capacitor Problem...HELP!!

An electron enters the lower left side of a parallel plate capacitor & exits at the upper right side making an upward curve. The initial speed of the electron is 4.00 x 10^6 m/s. The capacitor is 2.00 cm long, and its plates are separated by 0.150 cm. Assume that the electric field between the plates is uniform everywhere and find its magnitude.

So I understand that F=ma=qE. I also understand that I can use kinematics to find the acceleration and I can also use the mass of an electron to figure out the force. However, how do I find q? I'm so confused!!! Please help! Thanks!!

2. Jul 5, 2007

### Meir Achuz

q is the charge on an electron. Look it up in your text.

3. Jul 7, 2007

### chaoseverlasting

q=e=1.6x10^{-19} coulombs...

4. Jul 8, 2007

### huyen_vyvy

in the vertical direction, the electron has travelled 0.15 cm (from lower left corner to upper right corner). the initial speed in the vertical direction is 0
=> distance = a*t^2/2 (a= acceleration and t- time)
the time is found by: t= d/v (in horizontal direction) = 2 cm/ speed
so now you can find a, and then E.
Good luck.