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Homework Help: Electron velocity

  1. Aug 30, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculate the velocity of an electron with 3 eV energy. This electron is accelerated by a constant field of 10 V/cm (parallel to the electron velocity) for 0.1 cm. What is the new electron velocity?

    My other problem is the unit for the electric field . it bothers me: V/cm usually it is N/C
    2. Relevant equations
    .5*m*v^2

    Please can i have some suggestions?

    3. The attempt at a solution
    3eV=3 x 1.6E-19=4.8E-19 joules=1/2 mv^2, so v^2=4.8E-19/4.5E-31=1E12
    so v=10^6 metres/sec.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Aug 30, 2010 #2

    kuruman

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    Gold Member

    You should be aware of the fact that 1 V/m = 1 N/C. So 1 V/cm is how many N/C?
     
  4. Aug 30, 2010 #3
    100 N/C
    thank i forgot all those units!

    to find the final speed, i use the formula (Vfinal)^2-(Vinitial)^2=2a*(0.1 e-2)
    when i did I found Vfinal =1.03 e6 m/s

    the velocity difference i think is very small , it seems not right. did i do the question corretly?
    thank you
     
    Last edited: Aug 30, 2010
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