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Re: [Phys-L] physics and potatoes



I disagree that the instructor needs to tell students before the question
that it is a discussion question without a necessarily "correct" answer.
Students should be getting such questions regularly. Now after the
discussion it would be OK to say that the topic is open and that there may
not be just one "best" answer.

Most teachers give questions which are supposed to have just one best
answers and grade them according to that criterion. Again, this kills
thinking. Students need to learn that even in science there are uncertain
answers and that some things are debateable. Unfortunately all of their
experience in math and science has been to feed them correct answers and
never to have them come up against ambiguous answers. As a result they
think of measurements as absolute numbers. They want absolutely correct
answers using equations and are resistant to obviously inexact answers from
graphs or maps. This leads them to ignore methods that are more likely to
yield good answers reliably. After all equations are the fastest way to get
a wrong answer. But guidance by other methods can be very helpful when
using equations.

When posing a question, often there are a variety of answers depending on
the assumptions. So letting students make different assumptions can be a
good exercise. Then when a variety of answers are OK, as long as the
assumptions are explicitly made, students do not like this. They want black
and white answers. This shows up in politics where people want one correct
answer and are unwilling to say that a different answer might be correct, or
at least not necessarily absolutely incorrect.

So students need to have some confusion at various points. Lack of
confusion often means they are just memorizing things.

Actually there is research which shows that completely clear lessons do not
work as well as ones where there is some confusion. The trick is to not
have too much or unsolveable confusion. Students need to be prepared to
have things which may pose confusion. That type of situation is the most
common one in real life.

John M. Clement
Houston, TX


I must throw in my two bits worth. I have encountered many
such questions as a student and as an instructor. I generally
found them to be confusing and frustrating because 1. The
instructor didn't just come out and say the question is meant
to be a discussion question and 2. The instructor did not say
there may not be an exact, i.e. right or wrong answer. This
put me in a position of wondering is there an acceptable
answer? Then I would ask the teacher - what is the correct
answer with a response of "I don't know." or "I can't tell
you." I would spend so much time wondering what an
appropriate response to the question would be I would miss
important parts of the lesson that followed. I suppose one
should always be on guard for ill posed or open ended
questions questions but somewhere along the line it is really
helpful to the student to be given some guidance as to a
correct/i.e. reasonable response. There's nothing wrong with
saying it is an ill posed question from the git go.

If a student is constantly wondering "is this a discussion
question" or "is it learn a rote task question" the student
will often be focusing on the wrong aspect of the material
being presented. I see it all the time in teaching our lab
courses. In short, be careful how you present such questions
as well as be explicit in explaining your answers (or lack
thereof). Confusion is not always the student's fault.

Dan


On Jan 13, 2015, at 12:00 PM, phys-l-request@www.phys-l.org wrote:

Message: 2
Date: Tue, 13 Jan 2015 08:07:24 -0600
From: "John Clement" <clement@hal-pc.org>
To: <Phys-L@Phys-L.org>
Subject: Re: [Phys-L] physics and potatoes
Message-ID: <D5D6C8E27E9140CBBB7DF1DCAB277680@ClementPC>
Content-Type: text/plain; charset="us-ascii"

Hmmm. Is convection really minimized, as the air circulates around
the potato with or without foil? I would say the retention of
moisture is a big factor because evaporation can cool
things rapidly.
This may be the largest effect here. But since some cooks claim it
cooks faster in foil there may be other answers. As to Hewitt's
answer, it depends on what the cook wants, and is not just
a matter of physics.

I still say it is a discussion question which may not have
a unique answer.
As such it can be a very good question. It is an example
of an open
ended question. Only having students ponder questions
which have one
unique approved answer kills a lot of thinking skills. If
I used this
question, I would probably not tell them the "approved"
answer, but I
would try to get them to use good physics ideas rather than
everyday
reasoning, even if no definite answer emerges.

John M. Clement
Houston, TX

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