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Electron shot between plates (electric field)

  • Thread starter miroku2192
  • Start date
1. Homework Statement

I've been staring at this last problem for a while now...but i really don't get it. So if someone could explain to me how to do this, that'd be great. Thanks:

In Fig. 22-64, a uniform upward electric field E of magnitude 2.00 x 10^3 N/C has been set up between two horizontal plates by charging the lower plate positively and the upper plate negatively. The plates have length L = 10.0 cm and separation d - 2.00 cm. An electron is then shot between the plates from the left edge of the lower plate. The initial velocity of V(sub zero) of the electron makes an angle theta =45.0 degrees with the lower plate and has a magnitude of 6.00 x 10^6 m/s.
(a) will the electron strike one of the plates? (b) If so, which plate and how far horizontally from the left edge will the electron strike?

I'm really confused on this...so if someone could help that'd be great. I was never really good at physics.

2. Homework Equations

Relevant equations? There were none provided..?

3. The Attempt at a Solution

Can someone just point me in the right direction first? I'm a bit confused on how i'm supposed to go about even TACKLING the problem. Would i use the E= kQ/r^2 ? Since it's only one electron being acted on by the electric field? So it's like a point electric field thing?
 

Doc Al

Mentor
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Would i use the E= kQ/r^2 ? Since it's only one electron being acted on by the electric field? So it's like a point electric field thing?
No, that's the field produced by a point charge. You already know the field. You must find the force that the given field exerts on the electron. (What's the relationship between F, E, and q?)
 
No, that's the field produced by a point charge. You already know the field. You must find the force that the given field exerts on the electron. (What's the relationship between F, E, and q?)
Ohh...i see, so it's like a mix of electricity + projectile motions right? Because... F= Eq, and E is given, and q i know because it's the same for both protons + electrons right? something like -1.6 x 10^-19? Anyway, after i find the force in newtons, i can just set it up as F = mass x acceleration, figure out acceleration and use projectile motions stuff right? I'm a bit shakey on projectile motions stuff though...when it says "a magnitude of 6.00 x 10^6 m/s.", does that mean after i find out acceleration, the initial velocity value i use is 6.00 x 10^6 m/s ?
 

Doc Al

Mentor
44,767
1,045
Ohh...i see, so it's like a mix of electricity + projectile motions right? Because... F= Eq, and E is given, and q i know because it's the same for both protons + electrons right? something like -1.6 x 10^-19? Anyway, after i find the force in newtons, i can just set it up as F = mass x acceleration, figure out acceleration and use projectile motions stuff right?
Exactly right.
I'm a bit shakey on projectile motions stuff though...when it says "a magnitude of 6.00 x 10^6 m/s.", does that mean after i find out acceleration, the initial velocity value i use is 6.00 x 10^6 m/s ?
Yes, but realize that the initial velocity is at an angle, so you need to find horizontal and vertical components. Only the vertical component of motion is accelerated--just like with regular projectile motion.
 
Exactly right.

Yes, but realize that the initial velocity is at an angle, so you need to find horizontal and vertical components. Only the vertical component of motion is accelerated--just like with regular projectile motion.
Oh right...i have to split up the x components and y components...Thanks so much, i think i get this question now. I really appreciate ALL your help!
 

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