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Re: Zero with units?



At 3:49 PM -0400 9/16/04, Bob LaMontagne wrote:

??? Suppose I am trying to have a student find the displacement of an
object that has an initial position of "0" and a final position at 5
meters. The student would then be expected to subtract the dimensionless
position "0" from the dimensioned quantity of 5m. This is quite contrary to
the approach that most of us try to instill in the students, where only
terms of similar dimensions can be added or subtracted.

Am I simply misunderstanding the point?

This is one of the reasons why I don't get sweaty about the issue. We
can get tied into knots over this sort of thing and it doesn't
enhance the teaching of physics to do so. I want the students to
understand what they are doing. If including units with zeroes that
they come across helps that process, fine. I'm not going to penalize
them for it. On the other hand, if they are sophisticated enough to
know that units with a zero value are usually meaningless, then that
is also fine. I only insist that they put units on non-zero
dimensions. What they do with zeroes I leave pretty much up to them.

Hugh
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Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

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