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Homework Help: Archived Estimate nuclear energy generation rate (formula given) per unit MASS MASS?

  1. Nov 8, 2012 #1
    1. The problem statement, all variables and given/known data

    Consider energy generation in the Sun. Fusion through the pp cycle takes place within its core which has

    r = 0.2 Rs
    T = 1.3 x 10 ^ 7 K
    rho (density) = 1.1 x 10 ^ 5 kg m^-3
    X (total mass fraction of hydrogen) = 0.34

    The nuclear energy generation rate for the pp cycle (where T6 = T/10^6K and density has units of kg m ^ -3) is

    Epp = (0.241) (rho) (X^2) (T6 ^ (-2/3) ) exp (-33.8/(T6 ^ 1/3)) W kg ^ -1

    Estimate epp per unit mass mass.


    2. Relevant equations

    Epp = (0.241) (rho) (X^2) (T6 ^ (-2/3) ) exp (-33.8/(T6 ^ 1/3)) W kg ^ -1

    3. The attempt at a solution

    I subbed everything in:

    Epp = (0.241) (1.1 x 10 ^ 5) (0.1156) ( 13 ^ -2/3) exp (-33.8/ (13 ^ 1/3))
    (T6 is 13, because it says in the question that T6 = T/10^6K)

    and I got 3.186 x 10 ^ -4 as my final answer, I assume the unit is W kg ^ -1 because it was given in the formula.

    The bit I'm confused by is that in the question it specifies "estimate epp PER UNIT MASS MASS."

    That bit I havent a clue about... did I do it wrong?

    Thanks for any help!
     
  2. jcsd
  3. Feb 6, 2016 #2

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    W/kg is fine if the problem statement is "per unit mass" (or "per unit mass mass" which looks like a typo).
     
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