Q.Heavy stable nuclei have more neutrons than protons. This because of the fact that:

The assertion that nuclear forces are always attractive is false (they are repulsive at very short range), and the reason that the nuclear force is weak is also false (it is the strongest known force). Therefore both statements are false, and the correct option is (D).

The strong nuclear force is charge-independent: it acts equally between any pair of nucleons (proton or neutron) at the same separation, so $F_{pp} = F_{pn} = F_{nn}$.

Extra neutrons add to the short-range attractive nuclear force without adding to the long-range repulsive Coulomb force between protons, helping keep heavy nuclei bound.

The strong nuclear force is attractive between all nucleons (n-n, p-p, n-p) and is short-ranged, while the electrostatic (Coulomb) force between protons is repulsive and long-ranged, so it accumulates faster as the number of protons Z grows. In heavy nuclei, this growing Coulomb repulsion tends to destabilise the nucleus. Adding extra neutrons increases the total attractive nuclear force (more nucleon pairs bound by the strong force) without adding any extra Coulomb repulsion, since neutrons are uncharged. This is why heavy stabl …

(d) repulsive for distance $r < 0.8\ fm$. …

Both statements are true, and the greater strength of the nuclear force over the short range is exactly why it can overpower Coulomb repulsion.

Assertion (A) is correct: inside a stable nucleus, the attractive nuclear (strong) binding force between nucleons dominates over the electrostatic Coulomb repulsion between protons -- this is why nuclei with more than one proton remain bound. Reason (R) is also correct: nuclear forces are indeed much stronger (roughly 100 times stronger at s …

The nuclear force is short-range, charge-independent, saturating, and spin-dependent — of the given options only spin-dependence is a genuine property.

The strong nuclear force that binds protons and neutrons inside a nucleus has several well-established characteristics:

• It is the strongest known force in nature at nuclear distances (about 100 times the electromagnetic force).
• It is SHORT-RANGE: attractive for separations of about 1–2 fm, falling to zero beyond about 10 fm — it is NOT long-range like gravity or the electrostatic force.
• It is CHARGE-INDEPENDENT: the force between p–p, n–n, and p–n is (nearly) the same, so it does not depend on electric charge.
• It is SATURATED: a nucleon interacts strongly with only its nearest neighbours, not with every other nucleon in the nucleus — this is why the binding energy per nucleon becomes roughly constant for larger nuclei rather than growing indefinitely. …

The strong nuclear force that binds nucleons together is attractive in nature and has an extremely short range, of the order of a few femtometres.

The nuclear force holding protons and neutrons together in the nucleus is the strongest of the fundamental forces. Its key features are:

• It is attractive for distances greater than about 0.8 fm (it becomes strongly repulsive at very short distances, preventing nucleon overlap, but overall it must be attractive to bind the nucleus). …

Yukawa's meson theory explains the short-range, strong nuclear force between nucleons as arising from the exchange of π-mesons (pions).

The strong nuclear force that binds protons and neutrons together in a nucleus is fundamentally different from the electromagnetic and gravitational forces. Hideki Yukawa proposed that this force results from nucleons continuously exchanging virtual particles called π-mesons (pions), analogous to how the electromagnetic force between charges can be described in terms of photon exchange.

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