### pressure integral

(integral relating pressure to a gas's characteristics)

The **pressure integral** relates a gas's pressure to
particle momenta and density.

∞
P = 1/3 ∫ n_{p}pv dp
0

- P - pressure.
- p - momentum.
- n
_{p}dp - number of particles per unit volume with momentum *p*.
- v - velocity of the particle (with the given momentum).

This form applies to any particles with momenta, and can be applied
photons for light pressure as well as molecules.

(*mathematics,dynamics*)
https://astro.uni-bonn.de/~nlanger/siu_web/ssescript/new/chapter1-3.pdf

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