The order of the size of the nucleus and the Bohr radius of an atom,respectively,are:

Are the nucleons fundamental particles,or do they consist of still smaller parts? One way to find out is to probe a nucleon just as Rutherford probed an atom. What should be the kinetic energy of an electron for it to be able to probe a nucleon? Assume the diameter of a nucleon to be approximately $10^{-15} \ m$.

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.

The atomic mass number of an element is $\qquad$ .

Which of the following is true for a sample of $U^{235}$ and $U^{238}$ isotopes?

Two nuclei have their mass numbers in the ratio of $1: 3$. The ratio of their nuclear densities would be