The radius of the nucleus of an atom whose mass number is $125$ is:

$A$ neutrino is a particle,which is

Assertion $(A):$ Forces acting between proton-proton $(f_{pp})$, proton-neutron $(f_{pn})$ and neutron-neutron $(f_{nn})$ are such that $f_{pp} < f_{pn} = f_{nn}$.
Reason $(R):$ Electrostatic force of repulsion between two protons reduces the net nuclear force between them.

Calculate the height of the potential barrier for a head-on collision of two deuterons. (Radius of deuteron is $2$ fm).

$A$ nucleus (of nuclear density $\rho$) disintegrates into two daughter nuclei with masses in the ratio $8 : 27$. The density of the smaller nucleus is

The force acting between proton and proton inside the nucleus is