Among the fundamental forces, which one of the following is the strongest force?

$A$ nucleus splits into two nuclear fragments. If the ratio of their velocities is $2:1$,then the ratio of their nuclear radii is:

If a nucleus $D$ at rest breaks up into two fragments $A$ and $C$ which fly off with velocities in the ratio $8 : 1$,then the ratio of the radii of the fragments is

$A$ nucleus has mass number $\alpha$ and radius $R_{\alpha}$. Another nucleus has mass number $\beta$ and radius $R_{\beta}$. If $\beta = 8\alpha$, then $R_{\alpha}/R_{\beta}$ is:

Which of the following pairs of nuclei represents isotones?

Define nuclear force.