As long s the deformation is reversible, the force exerted by a compressed or stretched spring is called an elastic force.
Alas, in physics the word "elastic" has two different meanings, and I cannot figure out which meaning we are trying to define here.
The concept of "elastic limit" of a spring means there is no permanent deformation.
The concept of "elastic collision" means the process is thermodynamically reversible. No entropy is created.
In the context of section 8.6, it is common for springs and exceedingly common for ropes to have a great deal of internal friction, even in situations where the elastic limit has not been exceeded.
Specific suggestions:
Point out that there are two meanings. This is utterly nontrivial, because in the context of section 8.6 the notion of non-deformation makes sense, but later in section 10.5 on page 835 the same term (_elastic force_) is used to refer to non-dissipation.
Carefully define "elastic limit" (no deformation)
Carefully define "elastic collision" (no entropy production)
Find and remove all references to "_elastic force_" on the grounds that it is hopelessly ambiguous.
Don't define either meaning in terms of "reversibility", for the following reason:
One of the few pedagogical principles that people actually agree on says learning proceeds from the known to the unknown. It does no good to define thing B in terms of thing A unless the students have a firm prior understanding of thing A ... and in this case the students do not have a clear idea of what "reversibility" means ... certainly not one that is sufficient for present purposes.
In any case it doesn't make sense to define elasticity with one meaning and then use the term with the other meaning.
In section 8.6 on page 185 it says
Alas, in physics the word "elastic" has two different meanings, and I cannot figure out which meaning we are trying to define here.
In the context of section 8.6, it is common for springs and exceedingly common for ropes to have a great deal of internal friction, even in situations where the elastic limit has not been exceeded.
Specific suggestions:
One of the few pedagogical principles that people actually agree on says
learning proceeds from the known to the unknown. It does no good to define thing B in terms of thing A unless the students have a firm prior understanding of thing A ... and in this case the students do not have a clear idea of what "reversibility" means ... certainly not one that is sufficient for present purposes.In any case it doesn't make sense to define elasticity with one meaning and then use the term with the other meaning.