- #1

greypilgrim

- 547

- 38

Processes involving a friction force whose direction somehow depends on the direction of the velocity, such as ##\vec{F}=-\mu\cdot\vec{v}##, aren't symmetric with respect to time reversal. If you play it backwards, this force would be accelerating.

On the other hand, friction dissipates heat, and that increases entropy. So this is in agreement with thermodynamics.

I wonder: Is it really necessary to assume that friction dissipates heat to see that entropy is increased in such a process? Or is there a more direct or fundamental way to derive that the occurrence of a force like ##\vec{F}=-\mu\cdot\vec{v}## increases entropy, without getting into technicalities?