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Homework Help: Simple Question - Well I guess

  1. May 31, 2005 #1
    I just got up to this question which im stuck on an need a bit of help.
    Electron is accelerated by a potential difference of 10,000 volts
    1) What is the max velocity it will attain
    Now, I tried using the ke = 0.5 x M x V^2
    Just how do I convert Volts to joules and is that the correct formula Im using? Thanks.
  2. jcsd
  3. May 31, 2005 #2

    Chi Meson

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    You need to convert "electron-volts" (eV) to joules. The eV is the energy of one electron accelerated across one volt. To get to joules, you use the same number as the number of electrons in one coulomb (since a joule is a "coulomb-volt"). You will get a very small number for joules. THen proceed with the KE equation.
  4. May 31, 2005 #3
    1 eV = 1.6 x 10^-19 Joules
  5. May 31, 2005 #4


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    didn't you mean [itex] 1 eV \approx 1.6 \times 10^-19 [/itex] Joules
    or to better precision [itex] 1 eV \approx 1.60217646 \times 10^-19 [/itex] Joules
  6. May 31, 2005 #5
    Stop being so critical.

    [itex] 1 eV \approx 1.60217646 \times 10^{-19} [/itex] so youre both wrong.
  7. May 31, 2005 #6


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    Yes, that was what he meant- that was exactly what he said.

    And, of course, since the data was given to two significant figures, so was his answer!
  8. Jun 1, 2005 #7


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    Wanted to indicate to the questioner, that Doc's value is not absolute. :rolleyes:
    As you correctly alluded, it's rounded off.

    In my own experience, I've found it better not to round off until reaching the final answer. Even in academic questions, I've often encountered solution discrepancies due to accumulation of rounding errors.

    I wish to apologize to icedevilwoot on behalf of us (mentors) for this lengthy digression.
    I wonder how are you making out with your calculations? :smile:
    Last edited: Jun 1, 2005
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