Kinetic-Molecular Theory

Discussion

Postulates

• all matter is composed of microscopic particles (molecules in general, but also atoms, ions, and free electrons)
• molecules are very small relative to the distance between them
• molecules are in constant random (chaotic) motion
• collisions between particles are perfectly elastic

Macroscopic – Microscopic

• density is the sum of the mass of the molecules divided by the volume that the gas occupies
• pressure is a measure of the mean linear momentum of the molecules
• temperature is a measure of the mean kinetic energy of the molecules

〈K〉 = ³/₂kT

root mean square

[animate]

six modes of freedom

1. heave
2. sway
3. thrust
4. roll
5. pitch
6. yaw

degrees of freedom

• translational: radio frequencies
• rotational: microwave-infrared
• vibrational: infrared-visible-ultraviolet
• electronic: infrared-visible-ultraviolet-x ray

Photons created at the sun's center travel a distance of 2 × 10¹⁰ times the sun's radius before emerging. The trip takes something like 30,000 years.

The Physics Hypertextbook © 1998–2013 Glenn Elert

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