Physics · nuclei · NEET
No. The nuclear force is attractive for separations larger than about 0.8 fm, which is what binds nucleons together. But if two nucleons come closer than about 0.8 fm, the force becomes repulsive. This short-distance repulsion is why nucleons do not collapse into a single point and why the nucleus has a stable size. So the answer NEET wants is: mostly attractive, but repulsive at very small distances below 0.8 fm.
The nuclear force between two nucleons falls rapidly to zero once their separation is more than a few femtometres (1 fm = 10^-15 m). Beyond this range a nucleon feels no nuclear force from a distant nucleon. Compare this with the Coulomb force and gravity, which fall as 1/r^2 and reach across large distances. Because the nuclear force acts only over a few fm, each nucleon interacts only with its nearest neighbours - this is the reason for saturation.
No. The nuclear force is charge-independent. The force between neutron-neutron, proton-proton and proton-neutron pairs is approximately the same. This is very different from the Coulomb force, which acts only between charged particles. So a neutron (no charge) feels the nuclear force just as strongly as a proton does. NEET often tests this exact point.
Yes. The nuclear force is much stronger than the Coulomb (electrostatic) force and far stronger than gravity. It has to be strong enough to overcome the Coulomb repulsion between the positively charged protons packed inside the tiny nucleus. This large strength is what gives a binding energy of about 8 MeV per nucleon, which is much larger than the binding energy in atoms.
Saturation means each nucleon interacts only with a limited number of nearby nucleons (its neighbours within the short range), not with every nucleon in the nucleus. Because a nucleon deep inside is surrounded by the same number of neighbours regardless of nucleus size, its binding energy stays roughly constant. This is why the binding energy per nucleon is nearly constant (about 8 MeV) for medium nuclei with 30 < A < 170.
Unlike Coulomb's law (F proportional to 1/r^2) or Newton's law of gravitation, the nuclear force cannot be written as one simple equation. It is complicated: attractive at larger separations, repulsive at very small ones, and it depends on more than just distance. For NEET you only need to remember the statement 'the nuclear force has no simple mathematical form', not a formula.
It is the strongest of the basic forces, very short-range (a few fm), attractive above about 0.8 fm and repulsive below it, charge-independent (same for all nucleon pairs), it shows saturation, and it has no simple mathematical formula.
The nuclear potential energy is a minimum at about 0.8 fm. For separations larger than 0.8 fm the force is attractive; for separations smaller than 0.8 fm it becomes repulsive.
Experiments show the force between n-n, p-p and p-n pairs is nearly the same. This means the nuclear force does not depend on electric charge - it treats protons and neutrons alike.
Because of its short range, each nucleon binds only to nearby nucleons. So adding more nucleons does not change the binding energy of an inner nucleon much. This keeps the binding energy per nucleon nearly constant (about 8 MeV) for 30 < A < 170.
Yes, for NEET purposes. The force that binds protons and neutrons in the nucleus is called the strong nuclear force or simply the nuclear force. It is one of the fundamental forces of nature.
