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Re: [apcalculus] related rates
Posted:
Oct 8, 2012 11:38 PM


NOTE: This apcalculus EDG will be closing in the next few weeks. Please sign up for the new AP Calculus Teacher Community Forum at https://apcommunity.collegeboard.org/gettingstarted and post messages there.  Brett, et al 
The constant volume assumption is a reasonable mathematical model of rate of change in radius as a function of rate of change in length. It is perfectly appropriate for AP Calculus students because it allows them to concentrate on the calculus rather than on properties of realworld materials.
In the real world, this rate of change is measured by Poisson's ratio, which may differ from the constantvolume assumption. For a primer on this phenomenon, do a Google search. Wikipedia has a reasonably good explanadtion of the phenomenon.
Regards, Paul

"Brett Baltz" <brettbaltz@msdlt.k12.in.us> wrote:
> my class is making their own related rates problems. One group wants to > compare the rate of change of the length of a bungy cord to its radius > during a bungy jump. It is reasonable to do this through a constant > (cylindrical or otherwise) volume, right? > 
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