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Homework Help: Acceleration of electron in between charged plates

  1. Dec 8, 2009 #1
    dear.if the x-component and y-component of velocity is given i.e Vx &Vy.and E (electric field) is also given. then what equation should i use to find acceleration of the electron.
    i only know about E=F/e(relation of electric field and force)
    F=ma.if i want to find the "acceleration" if Vx ,Vy and E is given??
    anyone like to answer???
  2. jcsd
  3. Dec 8, 2009 #2
    Ok so if you just want to find the acceleration you only need E and the mass of the electron, which you can find on any physics text book, this is what google says. Mass of electron=9.10938188 × 10-31 kilograms. So now all you have to do is multiply E times the charge of an electron and you will get the Force and then use F=ma with the mass of the electron to find the 'a' acceleration. Now if the field is exactly on the X axis or the Y axis you will have to find out how much of the Force is in each direction using trigonometry. If it is perpendicular/parallel to either one then just do it normally

  4. Dec 11, 2009 #3
    you are rite dear... but if the X and Y component of velocity is given i think there must be role of this in acceleration... wht you say dear???
  5. Dec 11, 2009 #4


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    No, unless there is a magnetic field, the force is independent of the charge's velocity.
  6. Dec 11, 2009 #5
    But the acceleration depends upon the mass, and the mass increases with velocity per special relativity. I computed this problem in the mid 80's, so maybe I can search for my solution this weekend.

    As v increases, m increases, which influences a. The acceleration is not constant when v starts to exceed 10% of c. That is what I remember anyway. Does this help?

    Last edited: Dec 11, 2009
  7. Dec 11, 2009 #6
    um ya that is true but only when you start to approach c. a car traveling at 1000 m/s weighs the same as a car going 0 m/s but it starts to chang when it gets closer to c because the object cannot go past c so all the energy goes into making it heavier, or making it appear as if to have more mass. In all my physics problems I have never used the mass of the electron as changing, unless you are doing really high energy plates from which you could reach 99% of c or something close to that, it really shouldnt matter. Electrons are so tiny anyways that the fluxuation of its mass would be almost insignifigant i believe

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