Re: Can this be true?

[Bob Sciamanda <trebor@VELOCITY.NET>]

If you insist on the idealized model of the string as identical masses
connected by identical springs with identical "breaking tensions", and no
imperfections, then slowly and continuously stretching this model should
result in all springs failing at once!

-Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

"We have shown the symbol SQR(-1) to be void of meaning, or rather
self-contradictory and absurd." Augustus De Morgan in "On the Study and
Difficulties of Mathematics", 1831.


----- Original Message -----
From: Glenn A. Carlson <gcarlson@MAIL.WIN.ORG>
To: <PHYS-L@lists.nau.edu>
Sent: Thursday, August 12, 1999 10:44 AM
Subject: Re: Can this be true?
> What if the string had mass, but was horizontal?  Wht if the string was
> supported from below, not from above (the string is perfectly straight
> and plumb)?  What if the string is not acted on by gravity?  Change the
> assumptions; we change the answer.
>
> Real bodies break at imperfections (stress concentrations).  Perfect
> bodies don't break, or we wouldn't call them perfect.
>
> There is no paradox here.  The problem is accepting an idealization
> ("exactly the same all along") as describing reality ("a true
> statement").  We can reach any conclusion we want if we make
> sufficiently unrealistic assumptions.  It is quite easy to reach
> unrealistic conclusions from ideal (unreal) assumptions (e.g.,
> "perfectly incompressible fluid," "frictionless surface," "all things
> being equal," "if I were king of the world," "if pigs could fly,"
> etc.).
> . . .