How many of the following statements about the nuclear force are correct?
(A) The nuclear force between two neutrons is about the same as that between two protons.
(B) The potential energy of a pair of nucleons is a minimum when they are about 8 fm apart.
(C) Because the nuclear force is short-ranged, the binding energy per nucleon is nearly constant for \(30 \lt A \lt 170\).
(D) Two nucleons that are more than a few femtometres apart attract each other strongly through the nuclear force.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Two
The nuclear force holds protons and neutrons together inside a nucleus. It acts only over very short distances.
The statements that are correct:
Statement (A), same force for neutron-neutron and proton-proton pairs — correct
Statement (C), short range gives a nearly constant binding energy per nucleon — correct
The statements that are not correct:
Statement (B) — the potential energy is a minimum at about 0.8 fm. At 8 fm the nucleons hardly affect each other.
Statement (D) — beyond a few femtometres the nuclear force falls to zero.
Number of correct statements = 2
NCERT (2026-27):
Nuclear Force – “(iii) The nuclear force between neutron-neutron, proton-neutron and proton-proton is approximately the same. …”
Nuclear Force – “… The potential energy is a minimum at a distance r0 of about 0.8 fm. …”
Nuclear binding energy – “(ii) The constancy of the binding energy in the range 30 < A < 170 is a consequence of the fact that the nuclear force is short-ranged. …”
Nuclear Force – “(ii) The nuclear force between two nucleons falls rapidly to zero as their distance is more than a few femtometres. …”