change of tension formula

[Jamaureira]

Studying a rolling mill model I have found this equation:

dT/dt=k(V2-V1)

where
V1: strip velocity at point 1
V2: strip velocity at point 2
T: strip tension stress at a point between point 1 and point 2

Is that correct?
What principle of physics is it based on?

thanks,
JAM