#nuclear force

Radioactive Decay, Nuclear Forces and Stability

Why is the nuclear force considered saturated in large nuclei?

**Stability** belt of stability N≈Z for light, N>Z for heavy due to Coulomb, beyond leads to alpha decay, fission, stability requires balance, nuclear force saturated explains constant density and BE/A. The nuclear force is short-ranged, affecting only a fixed number of neighboring nucleons, so adding more nucleons in large nuclei does not proportionally increase the binding energy, leading to saturation. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.5 MeV, evaluation yields Limited range of interaction, consistent with Bohr model and nuclear binding

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

Which of the following best describes the nuclear force?

**Nuclear force** strong, short-range ~1 fm, attractive, charge independent, saturated in large nuclei because each nucleon interacts only with neighbors, not all others, so BE/A saturates ~8 MeV, primary factor limiting stable nuclei size is Coulomb repulsion between protons growing as Z² vs strong force saturating, beyond Z≈83 no stable nuclei, competition between Coulomb and strong. The nuclear force is a strong, short-range attractive force that binds protons and neutrons in the nucleus, overcoming the Coulomb repulsion between protons. It is much stronger than the Coulomb force and does n

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

Which property of the nuclear force leads to the saturation of binding energy in large nuclei?

**Radioactive decay** occurs when nucleus unstable, alpha decay emits He-4, beta decay neutron→proton+electron+antineutrino, gamma decay photon emission, decay law N=N₀ e^{-λt}, half-life T½=ln2/λ, nuclear density ~10¹⁷ kg/m³, nuclear force saturated means BE/A constant for A>20. The short-range nature of the nuclear force means it only affects nearby nucleons, not all nucleons in the nucleus, leading to a saturation effect where adding more nucleons does not significantly increase the binding energy per nucleon in large nuclei. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, B

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Hydrogen Atom Properties - Radius, Speed and Energy

Which of the following is true about the nuclear force at very short distances (less than 0.8 fm)?

**Hydrogen atom radius** r_n = n² a₀, a₀=5.3×10⁻¹¹ m first Bohr radius, r₂=4a₀=2.12×10⁻¹⁰ m, ratio r₄/r₂ =16/4=4, r₃=9a₀, circumference 2πr_n =2π n² a₀, for n=3 circumference=2π×9×5.3×10⁻¹¹=3×10⁻⁹ m. Orbital period T =2πr/v, v_n = v₁/n, v₁=2.2×10⁶ m/s, T₂=2πr₂/v₂, v₂=1.1×10⁶ m/s, T₂≈1.21×10⁻¹⁵ s. The nuclear force becomes strongly repulsive at distances less than 0.8 fm, preventing nucleons from collapsing into each other, as shown in the potential energy plot. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.5 MeV, evaluation yields It is strongly repul

Ref: NCERT > Physics Book > Atoms and Nuclei > Hydrogen Atom Properties - Radius, Speed and Energy

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Radioactive Decay, Nuclear Forces and Stability

Which force is responsible for overcoming the repulsion between protons in the nucleus?

**Nuclear force** strong, short-range ~1 fm, attractive, charge independent, saturated in large nuclei because each nucleon interacts only with neighbors, not all others, so BE/A saturates ~8 MeV, primary factor limiting stable nuclei size is Coulomb repulsion between protons growing as Z² vs strong force saturating, beyond Z≈83 no stable nuclei, competition between Coulomb and strong. The nuclear force, being much stronger than the Coulomb force, binds protons and neutrons together, overcoming the electrostatic repulsion between positively charged protons. Using E_n = -13.6/n² eV, r_n = n² a₀

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

Which statement best describes the nuclear force at distances greater than 0.8 fm?

**Nuclear force** strong, short-range ~1 fm, attractive, charge independent, saturated in large nuclei because each nucleon interacts only with neighbors, not all others, so BE/A saturates ~8 MeV, primary factor limiting stable nuclei size is Coulomb repulsion between protons growing as Z² vs strong force saturating, beyond Z≈83 no stable nuclei, competition between Coulomb and strong. At distances greater than 0.8 fm, the nuclear force is attractive and dominates over the Coulomb force, binding nucleons together until it drops off rapidly beyond a few femtometres. Using E_n = -13.6/n² eV, r_n

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

Which characteristic of the nuclear force explains its dominance over the Coulomb force in the nucleus?

**Nuclear force** strong, short-range ~1 fm, attractive, charge independent, saturated in large nuclei because each nucleon interacts only with neighbors, not all others, so BE/A saturates ~8 MeV, primary factor limiting stable nuclei size is Coulomb repulsion between protons growing as Z² vs strong force saturating, beyond Z≈83 no stable nuclei, competition between Coulomb and strong. The nuclear force is much stronger than the Coulomb force at short distances (within the nucleus), allowing it to overcome proton repulsion and bind nucleons together. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

Why does the nuclear force not distinguish between protons and neutrons?

**Stability** belt of stability N≈Z for light, N>Z for heavy due to Coulomb, beyond leads to alpha decay, fission, stability requires balance, nuclear force saturated explains constant density and BE/A. The nuclear force is charge-independent, acting equally between neutron-neutron, proton-neutron, and proton-proton pairs, as it is a fundamental property unrelated to electric charge. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.5 MeV, evaluation yields It is charge-independent, consistent with Bohr model and nuclear binding energy systematics.

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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Radioactive Decay, Nuclear Forces and Stability

What happens to the nuclear force when nucleons are separated by more than a few femtometres?

**Nuclear force** strong, short-range ~1 fm, attractive, charge independent, saturated in large nuclei because each nucleon interacts only with neighbors, not all others, so BE/A saturates ~8 MeV, primary factor limiting stable nuclei size is Coulomb repulsion between protons growing as Z² vs strong force saturating, beyond Z≈83 no stable nuclei, competition between Coulomb and strong. The nuclear force is short-ranged and drops rapidly to zero beyond a few femtometres, leaving only weaker forces like Coulomb repulsion or gravity to act between nucleons. Using E_n = -13.6/n² eV, r_n = n² a₀, L

Ref: NCERT > Physics Book > Atoms and Nuclei > Radioactive Decay, Nuclear Forces and Stability

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PHYSICS

Which of the following best describes the nuclear force?

The nuclear force is a strong, short-range attractive force that binds protons and neutrons in the nucleus, overcoming the Coulomb repulsion between protons. It is much stronger than the Coulomb force and does not depend on the electric charge of the nucleons.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Laws of Motion, Work Energy Power, Gravitation and System of Particles, Topic: Newton's laws, work-energy theorem and rotational dynamics.

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