Parallel Plate Electric Field: Electron Deflection and Emergence

[mvk1]

Parellel platers help :(

An electron with a velocity of 3.00 3 106 m/s [horizontally]
passes through two horizontal parallel plates. The magnitude of the electric field between the
plates is 120 N/C. The plates are 4.0 cm across. Edge
effects in the field are negligible.
(a) Calculate the vertical deflection of the electron.
(b) Calculate the vertical component of the final velocity.
(c) Calculate the angle at which the electron emerges

Diagram: http://img50.imageshack.us/img50/6418/problemo.jpg

Formulas: http://img339.imageshack.us/img339/186/formulae.jpg

Please feel free to use your own formulas as well.

 

[queenofbabes]

Well...your own thoughts? What have you worked out?

 

[mvk1]

ive tried to comprehend this but i am failing how do i find vertical deflection because d is already given

 

[queenofbabes]

What do you mean by d? Can you see that there will be a force causing the electron to be deflected? (Think attraction/repulsion)

 

[mvk1]

even if i calclate fe it is ont the distance of deflection..

 

[queenofbabes]

How would you find a distance from the force? Hint: For how long is the force acting on the electron?

 

[mvk1]

and when it says the plates are 4.0 cm across does it mean each plate or total plates

 

[mvk1]

F=qE
F=1.6x10^-19 C x 120 N/C
F=1.92x10^-17 N

 

[mvk1]

can someone please help..

 

[queenofbabes]

Good, you have your force. I'm sure what the question meant is that the length of the plates is 4cm, such that the horizontal distance traveled by electron under the influence of the E field is 4cm.

Now then, how would you find a distance from the force? Hint: For how long is the force acting on the electron?

 

[mvk1]

update:
i have found the accelaration using fnet =ma
since it is an electon mass is 9.1x10^-31
a=1.92x10^-17 N / 9.1x10^-31kg
a=2.1x10^13m/s2

BUT isn't this impossible ebacause it can't accelarate more than the speed of light

 

[queenofbabes]

Acceleration and speed cannot be compared like that. You simply can't travel faster than light. You can accelerate however quickly you want (as long as you have the force to do it)

You're on the right track.