The radius of a nucleus of a mass number $A$ is directly proportional to

In the nuclear reaction $_2He^4 + _zX^A \to _{z+2}Y^{A+3} + A$,$A$ denotes:

The strongest force in nature 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

Mark the correct statement.

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