D. We bring the body to rest in an adiabatic and isochoric way. There, the work
is performed. The state of the body is now given by the variables . The total work of the external forces is:
According to the first thermodynamic main-theorem, the work must be equal to . The second main-theorem additionally requires, that this difference is zero. Otherwise this circular process (or the reverse one) would represent a thermal perpetual motion machine. Thus we put in the previous expressions; then we notice that
and
thus we obtain:
or according to (2):
(6)
Thus we obtain the theorem: If an arbitrary body (in the state of rest) is under the pressure , then it