183_notes:examples:the_moment_of_inertia_of_a_diatomic_molecule

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183_notes:examples:the_moment_of_inertia_of_a_diatomic_molecule [2014/10/31 14:43] pwirving183_notes:examples:the_moment_of_inertia_of_a_diatomic_molecule [2014/11/05 20:40] (current) pwirving
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 === Facts === === Facts ===
 +
 +Mass of nitrogen atom is 2.3 x $10^{-26}$kg
 +
 +Average distance between nuclei is 1.5 x $10^{-10}$m
  
 === Assumptions and Approximations === === Assumptions and Approximations ===
 +
 +The distance between the atoms in the molecule does not change. 
 +
 +The model of the system you are using includes a spring between the atoms but these are not actual springs so the spring has no mass.
  
 === Lacking === === Lacking ===
 +
 +The moment of inertia of a diatomic nitrogen molecule $N_{2}$ around its center of mass?
  
 === Representations === === Representations ===
  
 +$I = m_{1}r^{2}_{\perp1}$ 
  
 +{{course_planning:course_notes:mi3e_09-018.jpg|?300}}
  
 === Solution === === Solution ===
  
-For two masses, $I = m_{1}r^{2}_{\perp1}$ + $m_{2}r^{2}_{\perp2}$. The distance between masses is d, so the distance of each object from the center of mass is $r_{\perp1} = r_{\perp2} = d/2$. Therefore:+For two masses, $I = m_{1}r^{2}_{\perp1}$ + $m_{2}r^{2}_{\perp2}$.  
 + 
 +The distance between the masses is d, so the distance of each object from the center of mass is $r_{\perp1} = r_{\perp2} = d/2$.  
 + 
 +Therefore:
  
 $I = M(d/2)^{2} + M(d/2)^{2} = 2M(d/2)^{2}$ $I = M(d/2)^{2} + M(d/2)^{2} = 2M(d/2)^{2}$
 +
 +Where you substitute in M for $m_{1}$ and $m_{2}$ as it is the same total mass we are talking about.
 +
 +Substitute in given values for variables.
  
 $I = 2 \cdot (2.3$ x $10^{-26}kg)(0.75$ x $10^{-10}m)^2$ $I = 2 \cdot (2.3$ x $10^{-26}kg)(0.75$ x $10^{-10}m)^2$
  
 +Compute moment of inertia of diatomic nitrogen molecule
 +
 +$I = 2.6$ x $10^{-46} kg \cdot m^2$
  
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