Quasistatic condition for a process involving a piston in a cylinder

[heyhey281]

The time scale on which the change (such as a change in external parameters or a external parameters or an addition of heat) takes place is referred to as τ_exp. The relaxation time τ_relax, on the other hand, is the time that the system needs to return to a state of equilibrium after a sudden change to return to a state of equilibrium. The condition quasistatic is fulfilled in the limiting case τ_exp/τ_relax → ∞

An example of a quasistatic process is the slow extraction of a piston from a thermally insulated cylinder filled with gas. How can I express this quasistatic condition with the piston velocity v and relaxation time τ_relax variables? In other words, my problem is if I only know the piston velocity v, how do I get τ_exp from this?

 

[anuttarasammyak]

By physical dimension analysis, how about
\tau_{exp}=\frac{V(t)}{Av} where V(t) is volume we are observing, A is area and v is speed of piston ? It’s time required to make up the current volume with the current piston speed.