🏐 Pressure = molecules drumming on the wall (Δp = 2 m v_x per bounce)

Watch molecules bounce elastically inside a cube of side L. When one strikes the shaded wall its x-velocity reverses, so it hands the wall momentum Δp = 2 m v_x. Add up all such kicks per second over the wall area and you get the pressure P = ⅓ n m ⟨v²⟩ = F/A.

Walkthrough 1 / 3

Molecules bounce elastically inside a cube of side L; the shaded red face is the wall we watch.

Number of molecules N 40

Temperature T 300 K

one bounce: Δp = 2 m v_x · wall: P = ⅓ n m <v²> = F/A
P = — kPa · Δp = — kg·m/s · bounces/s = —

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