The strongest force among the following forces in nature is

The force between a proton and a proton in a nucleus is .......

Two nuclei have their mass numbers in the ratio of $1: 3$. The ratio of their nuclear densities would be

The ratio of mass densities of nuclei of $^{40}Ca$ and $^{16}O$ is close to

Define $Z$,$A$,and $N$ by describing the structure of an atom.

Consider a nucleus ${ }_{30}^{60} X$. Its approximate density is (Take $1 \text{ amu} = 1.6 \times 10^{-27} \text{ kg}$, $R_0 = 1.2 \times 10^{-15} \text{ m}$)