$\pi$ mesons can be

The radius of a $_2He^4$ nucleus is $3 \, fm$. The radius of a $_{82}Pb^{206}$ nucleus will be .......... $fm$.

Two protons are kept at a separation of $40 \text{ Å}$. $F_{n}$ is the nuclear force and $F_{e}$ is the electrostatic force between them. Then:

An unstable heavy nucleus at rest breaks into two nuclei which move away with velocities in the ratio of $8:27$. The ratio of the radii of the nuclei (assumed to be spherical) is

How many neutrons are more than protons in the ${ }_{92}^{235} U$ nucleus?

The radius of a nucleus of mass number $64$ is $4.8 \text{ fermi}$. Then the mass number of another nucleus having radius of $4 \text{ fermi}$ is $\frac{1000}{x}$,where $x$ is . . . . . . .