Conservation of Momentum Principle

Steps:

• Recall that conservation of momentum states the total momentum in a closed system remains constant without external forces.
• Examine each option for alignment with this definition.
• Eliminate options that describe other physics concepts like force or elastic collisions.
• Select the option that precisely matches the principle's statement.

Why D is correct:

• It directly states the law: total momentum of interacting objects is constant if no net external force acts, as per Newton's first law extended to systems (p_total = constant).

Why the others are wrong:

• A: Describes Newton's second law (F = dp/dt), not conservation.
• B: Misstates elastic collision properties; relative velocity, not momentum, is conserved.
• C: Defines momentum (p = mv) but confuses it with collision outcomes.

Final answer: D