Re: [Phys-l] "Unlearning"

["John Clement" <clement@hal-pc.org>]

Significant figures can be used as a good hook to help students with math.
Many if not most students do not understand significant figures because it
is taught didactically.  Usually they have already gotten it in previous
science courses, and they didn't understand it then.  So if you have them
figure out how the result changes when you put in various values for the
missing digits, they begin to have a better understanding of math.  Actually
you treat 2.5 as a rounded off number that could be between 2.45 and 2.55.
Then the multiplication and addition rules become a lot clearer.  Also you
can then seque to the idea of errors so you can say that 2.5 has an
uncertainty of .05.

You don't have to go into STD or much in the way of statistics.  Many
students do get some statistics, but it was just a bunch of number games.
You can also have them check what happens when you average a list of 10
numbers, and then do it again omitting one value.  This can be done quickly
by having groups do just one omission, and then you can write the various
answers on the board.

But in the end, one has to pick the important topics.  But this one can be
an interesting exercise in "experimental math" and introduces students to
some elements of the experimental method.

John M. Clement
Houston, TX
> But if my physics or chem class is the last one that a student will ever
> take, I don't think I want to spend any of that time on the topic of
> significant figures at all.  It takes at least 2 or 3 days to "teach" the
> standard text-book version of that topic.  Kids HATE it and find it to be
> a painfully boring introduction to the subject at hand.  I'd rather just
> skip it, move on to content and tell them "give me three decimals in
> labwork and we'll worry about it later (or never)".  Those 3 days could be
> spent better (and would be hard to spend worse).