Electric potential no clue and midterm in 2 and a half hours

  1. 1. The problem statement, all variables and given/known data
    A proton is fired from far away toward the nucleus of an iron atom. Iron is the element number 26 and the diameter of the nucleus is 9.0fm. What initial speed does the proton need to just reach the surface of the nucleus? Assume the nucleus remains at rest.


    2. Relevant equations
    Conservation of energy which would get reduced to Ki=Uf
    U=kq1q2/r
    kinematic equation
    K = 1/2 m v^2
    Do some thing with the element number 26... has 26 protons so make a field?????


    3. The attempt at a solution
    Oh gosh. K this is completely wrong but ill just throw it out there for kicks.
    Ki=Uf
    Since i dont knwo what r is since its sperical and that confuses me.... ill guess you use the distance on the surface of the nucleus?
    1/2mv^2 = kq1q2/r
    1/2 (1.67E-27) v^2 = 9E9 (1.6E-19) (26*1.6E-19) / 4.5fm
    v = 350192

    the answer is 3.99E7

    Thank you!!!!
     
  2. jcsd
  3. Doc Al

    Staff: Mentor

    This is perfectly correct, just redo your arithmetic. (Change fm to standard units.)
     
  4. Seriously?!? thanks!!!!!
    Im a mess!!! :S
    You wouldnt happen to know and equation concerning the diameter of a wire with lenght and current and all that jazz would you??
     
  5. Doc Al

    Staff: Mentor

    Not sure what you're asking. If you post a complete problem, I can take a look.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?