A nucleus at rest splits into two nuclear parts having same density and the radii in the ratio $1 : 2$ . Their velocities are in ratio ———

Assertion : Isobars are the elements having same mass number but different atomic number.
Reason : Neutrons and protons are present inside nucleus.

$STATEMENT-1$: The plot of atomic number ( $\mathrm{y}$-axis) versus number of neutrons ( $\mathrm{x}$-axis) for stable nuclei shows a curvature towards $x$-axis from the line of $45^{\circ}$ slope as the atomic number is increased. and  $STATEMENT-2$: Proton-proton electrostatic repulsions begin to overcome attractive forces involving protons and neutrons and neutrons in heavier nuclides.

The radius of $R$ of a nucleus of mass number $A$ can be estimated by the formula $R =\left(1.3 \times 10^{-15}\right) A ^{1 / 3}\, m .$ It follows that the mass density of a nucleus is of the order of

$\left( M _{\text {prot. }} \cong M _{\text {neut. }}=1.67 \times 10^{-27} kg \right)$

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