Re: [Phys-l] Zero

["Cliff Parker" <cparker@charter.net>]

I like the ideas expressed in this thread.  I hope you will allow me to add 
my two cents worth.  I teach high school physics.  When I ask my students to 
tell me what 0/0 or 3/0 etc. is they of course tell me that it is 
meaningless.  When I ask them why it is meaningless 90%+ can only back it up 
with because that is what my math teacher told me.  At least at the level I 
am teaching I think the question of the meaning of such quantities needs to 
be chewed on by my students more than most have chewed.

Along the same lines.  A question came up the other day in class about the 
meaning of a vector of zero magnitude.  What direction is it pointing?  Can 
we really call such a thing a vector when its direction is indeterminate and 
if so why?  Because my teacher told me so doesn't count.

Cliff Parker

----- Original Message ----- 
From: "John SOHL" <JSOHL@weber.edu>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Saturday, October 13, 2007 4:10 PM
Subject: Re: [Phys-l] Zero


> The answer is NO. But that is for the "definitive" part of your question. 
> The whole point of L'Hospital's Rule in calculus is to address the issue 
> of two functions going to zero with one of those functions divided by the 
> other. The question becomes one of "who gets to zero first."
>
> For example, the sinc(x) function, which is defined as sinc(x) = sin(x)/x 
> is equal to 1 when x= 0. Thus for x=0 you have the case which you 
> describe:
> sin(x)/x = sin(0)/0 = 0/0 and the answer is 1 by L'Hospital's Rule.
>
> The sinc(x) function is very common in optics when calculating diffraction 
> patterns for slits.
>
> In general there is no fixed or "definitive" answer for 0/0, you must know 
> how you have approached that point.
>
> Other functions for 0/0 will reach other values including zero and 
> infinity. In the end, L'Hospital's Rule, rules! :-)
>
> John
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> John E. Sohl, Ph.D.
> Professor of Physics
> Weber State University
> 2508 University Circle
> Ogden, UT 84408-2508
>
> voice: (801) 626-7907, fax: (801) 626-7445
> e-mail: jsohl@weber.edu
> web: http://physics.weber.edu/sohl/
>
> > > > JMGreen <jmgreen@sisna.com> 10/12/2007 4:19 PM >>>
> Has the fraction zero/zero a definitive answer?
>
> Is there a book named "Zero" which purports a definitive answer?
>
> Jim
>
> J M Green
> Email:  MailTo:JMGreen@sisna.com
> WWW: http://users.sisna.com/JMGreen
>
>
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