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Homework Help: Finding a B-field.

  1. Aug 25, 2007 #1
    given is:
    http://img340.imageshack.us/img340/6684/oplosqa0.jpg [Broken]

    So if you have a question with a B-field you need any speed given from the particles who entering in this field.
    Who can I find this speed? Thanks.
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Aug 25, 2007 #2

    learningphysics

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    Get the speed from the kinetic energy 100keV.
     
    Last edited by a moderator: May 3, 2017
  4. Aug 25, 2007 #3
    I try this but I fail so:

    [tex]\frac{1}{2}m . v^2=U[/tex]
    then we have
    [tex]1,602 \ . \ 10^{-19} \ . \ 1 . \ 10^5=1,602 \ . \ 10^{-14}= \frac{1}{2} 10^{-27}.v^2 [/tex]

    so [tex]v[/tex] must be [tex]\sqrt{ \frac{2 \ . \ 1,602 . 10^{-14} } {10 ^{-27} } }[/tex]

    is this correct?
     
  5. Aug 25, 2007 #4

    learningphysics

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    mass of a proton = [tex]1.67*10^{-27}kg[/tex]. Other than that everything looks good.
     
  6. Aug 25, 2007 #5
    Thanks.
     
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