Equipartition of energy

Imagine that elastic balls (or atoms and molecules) are confined in a container. They undergo elastic collisions with the walls and with themselves.

The requirement to conserve both momentum and kinetic energy in the collisions leads to a simple outcome.

As time passes the average total kinetic energy of each class of particles approaches the same value. If hydrogen and oxygen are confined in the same container, at equilibrium, the average kinetic energy of the hydrogen atoms is the same as the average kinetic energy of the oxygen atoms.

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The equipartition of energy leads to the definition of absolute temperature and the Ideal Gas laws.

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