Name the following molecule (common name and IUPAC)?

No you don't. Try again.

 

Here is sec-pentylalcohol and sec-pentylbenzene.

sec-pentyl(stuff) isn't well-defined.

 

yes, the two systems are 2-pentylcyclohexane and 3-pentylcyclohexane.

These are both common and IUPAC names.

The sec- iso- tert- type names are confusing and only really useful for industrial compounds commonly known by these names or chains of 4 or fewer carbon atoms. For pentyl systems, the traditional nomenclature is even more confused by the intrusion of "amyl"

"Common" or "industrial" names are not really worth knowing these days unless you are working with shipments of stuff. There are about 20 isomers of octane. n-octane is the straight chain isomer. There is no possible way you could know without looking it up or working with it that iso-octane is 2,2,4-trimethylpentane!

 

I think you'll find that where you are presented 'sec-' or 'tert-' substituted alkanes there will be only one obvious answer. Sec-butylcyclohexane is unambiguous since the cyclohexyl substitution at either secondary carbons results in a single product. That isn't the case with sec-pentylcyclohexane. Substitution at either the 2 or the 3 position is correct for that name so the ambiguity resulting from that nomenclature will result in misidentification or miscommunication and shouldn't be used.

BTW, a typical test question reads, "The name sec-butyl alcohol defines a specific structure but the name sec-penty alcohol is ambiguous. Explain."

So now you know.

 

Tongue in cheek and only very marginally relevant to the OP question :-

Another test question: "The name sec-butyl alcohol does not unambiguously define a single substance. Nor does the IUPAC designation 2-butanol. Explain why not, and how to rectify the nomenclature."