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Position,velocity, speed, direction of travel of an electron

  1. Sep 16, 2013 #1
    1. The problem statement, all variables and given/known data
    As an example of the manipulation of an electron beam, consider an electron traveling away from the origin along the x axis in the xy plane with initial velocity vi hat bold = vii hat bold. As it passes through the region x = 0 to x = d, the electron experiences acceleration a = axi + ayj, where ax and ay are constants. For the case vi = 1.93 multiplied by 10^7 m/s, ax = 8.88 multiplied by 10^14 m/s2, and ay = 1.48 multiplied by 10^15 m/s2, determine the following, at x = d = 0.0100 m.
    a)Find the position of the electron
    b) the velocity of the electron
    c) the speed of the electron
    d)the direction of travel of the electron



    2. Relevant equations
    For a, i tried using the equation Yf=1/2ayt^2
    but the answer was wrong and I dont know if i used the wrong equation/numbers
    b-d i dont know where to start
    3. The attempt at a solution
    I used above equation and got -0.000235
     
    Last edited: Sep 16, 2013
  2. jcsd
  3. Sep 16, 2013 #2

    gneill

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    Staff: Mentor

    Start by concentrating on the motion in the x-direction since you're given the distance of travel. It may be easier to determine the x-direction speed first, then find the time of travel.

    So, what other equation of motion do you know that relates the initial and final speeds with acceleration and distance?
     
  4. Sep 16, 2013 #3
    Wouldnt that be Vxf^2=Vxi^2+2ax(xf-xi)?
     
  5. Sep 16, 2013 #4

    gneill

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    Staff: Mentor

    That would be the one. What do you get for the final speed of the electron in the x-direction?
     
  6. Sep 16, 2013 #5
    Well if I did everything right, I got 1.93x10^7 m/s
    ????
     
  7. Sep 16, 2013 #6
    wait but thats the same as Vi
     
  8. Sep 16, 2013 #7

    gneill

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    Staff: Mentor

    Yes, so that can't be right (unless the acceleration is insignificant, which it isn't in this case).

    Perhaps you should show the work in detail.
     
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