Two protons exert a nuclear force on each other. The distance between them is approximately:

The range of the nuclear force is

If the nuclear forces between two protons,two neutrons,and a proton-neutron are denoted by $F_{pp}$,$F_{nn}$,and $F_{pn}$ respectively,then:

The unit of length convenient on the nuclear scale is a fermi: $1 \; f = 10^{-15} \; m$. Nuclear sizes obey roughly the following empirical relation: $r = r_{0} A^{1/3}$,where $r$ is the radius of the nucleus,$A$ is its mass number,and $r_{0}$ is a constant equal to about $1.2 \; f$. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of a sodium nucleus.

$A$ heavy nucleus is unstable for any value of $\frac{N}{P}$ because

Given the mass of an iron nucleus as $55.85 \, u$ and $A=56$,find the nuclear density.