Nuclei

Q1.Which of the following statements about nuclear forces is correct?

• ANuclear force acts over long distances like gravity
• BNuclear force is always attractive and charge-dependent
• CNuclear force is short-range, charge-independent, and repulsive at distances < 0.8 fm
• DNuclear force is weaker than electromagnetic force at all distances

Q2.The nucleus of an atom consists of:

• AProtons and electrons
• BProtons and neutrons
• CNeutrons and electrons
• DProtons, neutrons, and electrons

Q3.In a chain reaction with U-235, the multiplication factor k = 1 means:

• AThe chain reaction is growing exponentially
• BThe chain reaction is dying out
• CThe chain reaction is self-sustaining at a constant rate (critical condition)
• DEach fission event causes exactly 235 subsequent fissions

Q4.A radioactive element has a decay constant λ = 0.693 per day. Its half-life is:

• A0.693 days
• B1 day
• C2 days
• D0.5 days

Q5.The density of nuclear matter is approximately:

• A10⁷ kg/m³
• B10¹² kg/m³
• C2.3 × 10¹⁷ kg/m³
• D10²⁴ kg/m³