= Entropy gain from impact and thermal equilibration
A body of mass $m$, <heat capacity> $c$, <temperature> $T_i$ and speed $v$ that stops in a large reservoir at $T_L$ produces <entropy> $mc[\log(T_L/T_i)+T_i/T_L-1]+mv^2/(2T_L)$, assuming constant <heat capacity> and no phase changes. The first term follows by adding the body's logarithmic <entropy> change to the reservoir's <heat> gain; the second is kinetic-energy dissipation. A numerical answer needs the reservoir <temperature>.
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