# Archived Estimate nuclear energy generation rate (formula given) per unit MASS MASS?

1. Nov 8, 2012

### daleklama

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. Feb 6, 2016

### Staff: Mentor

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