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\sect{Pressure of gas in a box with gravitation}

A gas given in a gravitation field. Use the former exercise to write
the distribution function ${Z_{N}\left(\beta, Z_{a}, Z_{b}\right)}$.

Calculate the forces (in their absolute value) that work on the
lower sidewall ${\left(F_{a}\right)}$ and on the upper sidewall
${\left(F_{b}\right)}$ of the box.

What is the difference between those forces?! explain the result you
get.