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Re: Cable around the Equator
Posted:
Nov 5, 1996 4:08 PM


Not only was his math impeccable, it was also correct! I think that it passes correctly the sanity check, where is the problem?
Juan Miguel Vilar
On 5 Nov 1996, mfr1 wrote:
> How can adding 50' of slack to the cable spread evenly around the equator > add 8' at each point? Your math was impeccable but your answer does not > pass the sanity check! This is why we must not blindly accept mathematical > results. That is the lesson to be learned from this geometry problem. > > lipp@educ.umass.edu wrote in article > <Pine.PMDF.3.91.961104130200.557939369A100000@oitvms.oit.umass.edu>... > > > > > > On Mon, 4 Nov 1996, mfr1 wrote: > > > > > Ma Bell wants to place a telephone cable around the equator. She adds > 50 > > > feet to the length of the cable beyond what is required. This slack in > the > > > cable allows the cable to be strung up above the ground. How high up > from > > > the surface of the earth will the cable stand? You can assume that the > > > earth is a perfect sphere. > > > > > > In your mind, run a sanity check on your answer to see if it makes > sense. > > > > > Surprisingly, you will be able to walk under the cble easilty. Since the > > > circumference of a circle is C = 2piR, each increase in R obf 1 foot > > increases the circumference by 2pi feet. since the cable has been > > increased by 50 feet the radius of the cablecircle will be increased by > > 50/2pi or about 8 feet! > > > > Alan Lipp > > >



