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#gas dynamics

2 public questions tagged with this topic.

In a longitudinal wave traveling through a gas, what is the relationship between displacement nodes and pressure antinod

**Quantization due to boundaries** leads to discrete harmonic series. Frequency difference between harmonics is f₁, so f₃ - f₁ = 2f₁ = v/L. Understanding node-antinode pattern explains resonance and overtones in strings. In longitudinal waves, displacement nodes (zero displacement) occur where particles are maximally compressed or rarefied, leading to maximum pressure variation (pressure antinodes). Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields They occur at the same points, illustrating frequency-length-speed interdependence and quantizatio

Ref: NCERT > Physics Book > Waves > Stationary Waves and Standing Waves in Strings

What is the time between collisions for a gas molecule with a mean free path of 4.5 × 10⁻⁷ m and average speed of 450 m/

**Ideal gas internal energy** proportional to temperature, U = (f/2) R T per mole, monatomic 3/2 R T, diatomic 5/2 R T, change ΔU = f/2 n R ΔT, for temperature increase internal energy rises, explaining why heating gas at constant volume raises U entirely as heat. tau = (l)/() = 4.5 × 10⁻⁷/4⁵⁰ = 1.0 × 10⁻⁹ s. Substituting values gives 1.0 × 10⁻⁹ s, which matches expected kinetic theory result, confirming mean free path λ = 1/(√2 n π d²), ideal gas law P V = n R T and v_rms = √(3 R T/M) relations.

Ref: NCERT > Physics Book > Behaviour of Perfect Gas and Kinetic Theory > Internal Energy of Ideal Gases