Re: [MATHEDCC] The Potato Salad Problem
Wayne Mackey (wmackey@COMP.UARK.EDU)
Fri, 11 Apr 1997 14:23:07 -0600
>At 10:04 AM 4/9/97 U, you wrote:
>>I really like problems like this one for its unexpected answer. I often use
>>them (realistic or not) to suggest that we should not always trust our
>>intuition. This is always interesting in the midst of a discussion on
>>"intuitive" limits.
>>
>>Another good one involves assuming the earth is a sphere with a circumference
>>of 25,000 miles. (I know this is not realistic, but it gets worse.) Stretch
>>a string around the equator so that it exactly touches the surface of the
>>earth at all points. In other words, take a 25,000 mile long string and put
>>it around the earth at the equator. Then add 10 FEET (emphasis intended) to
>>the string and form a new larger circle of string that is equidistant from the
>>earth at every point. How far above the surface of the earth is the new
>>string?
>>
>
>I was first presented this problem in a graduate Math Ed course 20+ years
>ago (boy, what a memory!!). It was presented with this twist: If you added
>50 feet of string to the string stretched around the equator, would it get
>far enough off the surface of the earth for an average sized adult male to
>crawl under it? If not, estimate how much string you would have to add.
>
>And my, how times have changed. After doing that problem for homework, the
>next day we were asked how far a string would rise off the surface of a
>tennis ball if 50 feet were added to its length (same situation). So we
>were then given the problem to prove that the "new" diameter was a function
>only of the "new" length, not of the "old" diameter and to find the equation
>relating them. (Does anybody 'prove' anything anymore? ;-) )
>
>
>
>>Jerry Thornhill
>>jerry_thornhill@sw.cc.va.us
>>Southwest Virginia Community College
>>Richlands, VA
>>
>I almost assigned a proof as a group project in my finite math class but I
>chickened out. That might be significant.
wayne
Wayne F. Mackey
Director, Math Resource Center
University of Arkansas
P.O. Box 2441
Fayetteville, AR 72702
(501) 575-7661
(501) 582-3764
wmackey@comp.uark.edu
http://comp.uark.edu/~wmackey
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