Wall Collisions → Pressure

Gas molecules collide with container walls — these collisions create pressure.

Assume collisions are ELASTIC: kinetic energy and momentum conserved.

When molecule hits wall, momentum component perpendicular to wall REVERSES (Δp = 2m·v_perp).

Number of collisions per unit time per unit area = (1/4)·n·⟨v⟩, where n = number density.

Total force on wall = rate of momentum transfer = pressure × area.

Pressure P = (1/3)ρ·v_rms² — derived from kinetic theory.

Higher T ⇒ higher v_rms ⇒ higher pressure (at constant V, n).

Reflection assumed specular (angle of incidence = angle of reflection); real walls may have more complex interactions.