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Re: websites

I checked out the site you listed. It does cantain a disclaimer saying
that the authors are pre-college students, and that the information in
the sites may not be correct. The disclaimer was posted so it was hard
to avoid, but the text was small and not easily readable.
Given the intent of the site, I'm not sure what else the webmaster could
do.

cheers

On Thu, 27 May
1999, Doug Craigen wrote:

I have been following the thread on websites and want to add a word
of caution. Here is an excerpt from the site:
<http://library.advanced.org/11902/physics/momentum.html>
The discussion is about a bat hitting a baseball and concludes:

"Now, you may have noticed that I said momentum is "almost"
conserved. Why isn't it if the equations say it should be? Well,
momentum is only conserved if the materials involved in the
collision are inelastic or inflexible (perfectly solid). Although you
might assume that bat and the ball are inelastic materials, they
are not. When the ball hits the bat, the ball will be squished to a
certain degree. After few milli-seconds, it rebounds back. This
contraction action will use up some energy, making conservation
of momentum false. There are also factors that can use up
energy, however, the concept of conservation of momentum is still
relevant in predicting the range of a baseball."

We are just covering conservation of momentum in the non-calculs intro
physics I'm teaching this summer at the University of Winnipeg. I shall
have to make sure that this site does NOT appear on my list of class
resources. Its hard to be become editor for every web site that looks
worthwhile, on the other hand this example illustrates the dangers in
not doing so. One can always *hope* that at least on of the students
would come to me and say "I'm a bit confused about one of the web pages
you refered us to...".

()-()-()-()-()-()-()-()-()-()-()-()-()-()-()-()

Doug Craigen
Latest Project - the Physics E-source
http://www.dctech.com/physics/