Molecular inertia makes air particle velocity change smoothly and continuously

Evidence

Then the golf balls will start moving with a velocity away from each other in order to get to the rarefacted state. Again the velocity toward the golf balls will become zero at the trough of the rarefaction. The velocity does not switch instantly from one direction to another, due to the inertia of the molecules involved; instead it accelerates smoothly from a stationary to a moving state and back again. The velocity component reaches its peak between the compressions and rarefactions, and for a sine wave displace­ ment component the associated velocity component is a cosine. — David Howard, Jamie Angus, coustics and Psychoacoustics, 144

Categorization

• DEFINE: Explains how velocity relates to displacement in a traveling sine wave — foundational for understanding sound propagation.
• corroborated: 2 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 144
• XREF: connects to: Air is a seething low-density molecular gas with constant collisions; The Bernoulli effect couples airflow velocity to reduced pressure at constrictions; Medium inertia produces a time lag in disturbance propagation through a material (+2 more)

Broader Connections

• Medium inertia produces a time lag in disturbance propagation through a material #expands (0.85)
• Sound wave molecules have zero velocity at compression peaks due to inertia #expands (0.80)
• Inertia delays wave transmission and the medium returns to rest afterward #expands (0.80)