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Too general calculation of oscillation freq of hydrogen molecule

  1. Oct 3, 2010 #1
    1. The problem statement, all variables and given/known data

    Okay here's the problem, normally I can get all this stuff, but right now this is blowing my mind, partly because its too general.

    "In other problems and examples in the textbook we found the effective spring stiffness corresponding to the interatomic force for aluminum and lead. Let's assume for the moment that, very roughly, other atoms have similar values.

    (a) What is the (very) approximate frequency f for the oscillation ("vibration") of H2, a hydrogen molecule containing two hydrogen atoms? Remember that frequency is defined as the number of complete cycles per second or "hertz": f = 1/T. There is no one correct answer, since we're just trying to calculate the frequency approximately. However, just because we're looking for an approximate result doesn't mean that all answers are correct! Calculations that are wildly in disagreement with what physics would predict for this situation will be counted wrong.
    f = _____cycles/s (hertz)"

    2. Relevant equations

    im using f = (1/T) = omega/2pi

    and omega = sqrt(K/m), K being the spring constant, (or interatomic bond strength) and m being the mass of the object


    3. The attempt at a solution

    okay well first of all I just went and looked up the real answer because we never actually calculated the spring stiffness for aluminum or lead earler.

    I put in, 8.03e14 cycles/s (hertz), but apparently the real answer is incorrect.

    So I look in the textbook, and we have solved to find the interatomic bond strength of copper atoms, which was 20.6 N/m. So then I did

    f = sqrt(K/m)/2*pi

    sqrt(29.6/(2*1.674e-27))/(2*pi)

    1.674e-27 being the mass of a hydrogen atom.

    So I got 1.4965e14, which again was wrong!

    Can someone help me out?
     
  2. jcsd
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