Re: physics/pedagogy of coffee-mixing

[Chuck Britton <cvbritton@TELOCITY.COM>]

At 12:47 PM -0400 6/25/00, Ludwik Kowalski,  you wrote about Re:
physics/pedagogy of coffee-mixing:


> John Denker wrote:
>
>  > Suppose you have a cup of coffee and a cup of tea.  In step 1,
>  > you transfer one spoonful of liquid from the coffee-cup to the
>  > tea-cup.  In step 2, you transfer one spoonful of liquid from
>  > the tea-cup back to the coffee-cup. Question:  Is there more
>  > tea in the coffee, or more coffee in the tea?
>
> I never heard this question. So let me show how I would answer.
> Model each cup as an urn with 1000 balls, black for the coffee and
> red for the tea. Suppose one spoonful means 10 balls and that good
> mixing occurs after the first transfer. Also that volumes of coffee
> and tea balls are identical. Pure water balls are white and can be
> ignored in this problem.

I think that Ludwig and others might want to consider a few more
coffee/tea molecules that have been dissolved in the fixed volumes of
water.
               (Like maybe tea is at LEAST a .001 molar solution?)

I am useing this as an example of how I try to BOTHER my students as
opposed to giving them the answer.
I can't claim to a Socratic teacher but I DO hope to get them
involved in the reasoning process AND it behooves me to try to
understand where their 'incorrect' reasoning is coming from.

  -.     .-.     .-.     .-.     .-.     .-.     .-.     .-.     .-.     .-
    \   /   \   /   \ N /   \ C /   \ S /   \ S /   \ M /   \   /   \   /
     `-'     `-'     `-'     `-'     `-'     `-'     `-'     `-'     `-'
Chuck Britton                                   Education is what is left when
britton@ncssm.edu                               you have forgotten everything
North Carolina School of Science & Math         you learned in school.
(919) 286-3366  x224                            Albert Einstein,        1936