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Homework Help: J shock in a gas for gamma = 7/5

  1. Jan 25, 2009 #1
    1. The problem statement, all variables and given/known data

    For the case of a strong shock propagating into a gas with [tex]\gamma=7/5[/tex] What is the ratio [tex]\rho2/\rho1[/tex]

    2. Relevant equations
    [tex]\rho\ u=constant[/tex]

    [tex]P+ \rho\ u^2=constant[/tex]

    [tex]\frac{1}{2} u+ \frac{\gamma }{\gamma -1}\frac{\ P}{\rho} = constant [/tex]

    3. The attempt at a solution

    I can use the 3 equations in this form to get [tex]\rho2/\rho1=6[/tex] but my problem is how do I arrive at the 3rd equation in the given form

    we were given equation 3 in the form [tex]\frac{1}{2} u+ \frac{5}{2}\frac{\ P}{\rho} = constant [/tex] but this is only valid for [tex]\gamma=\frac{5}{3}[/tex]

    I would like some advice on how to prove the adaption of equation 3 for different values of [tex]\gamma[/tex]
    Last edited: Jan 25, 2009
  2. jcsd
  3. Jan 28, 2009 #2
    Hi oro,

    Apologies but I don't quite understand what you're question is. If you wanted to solve the Rankine-Hugoniot condition for energy flow for something other than a monatomic gas, what's the problem with just plugging in a different value of [tex]\gamma[/tex] into equation 3 in your list?
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