Calculating Fermi Energy for Neutrons Confined to a Nucleus

[viviane363]

I am wondering about something:
Calculate the Fermi energy for the neutrons confined to a nucleus with 40 protons and 50 neutrons which roughly forms a sphere of radius 4.6 10^(-15) m.
the formula of the fermi Energy is EF= ((h-bar)^2*(3*pi^2*n)^(2/3))/2m
m:mass of electron, n = number density of electron
Then, in the problem we are given protons and neutrons. Where does influence the formula? and where do we use the radius there is one relation that is n = N/V ( N= protons+Neutrons)
is it right?
Also, do we use the mass of electron or the mass of proton = neutron this time?

 

[DrClaude]

The number of protons is not directly relevant to the question (it will of course affect the volume of the nucleus). Indeed, $n= N /V$. And you need to use the mass of the actual particle you are considering, namely the neutron.