Thanks for the many comments and suggestions to my N2 question.
Just to clarify, I am not against having my students analyze an Atwood
type apparatus and they all do it after we have become comfortable with
N2.
My concern is, doesn't one have to use N2 to analyze an Atwood and
therefore make such a lab experiment simply circular logic? I was
looking for a way to have them verify N2 without assuming N2 and do this
early on in their exposure to N2.