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How Good Is Your Intuition? (Mind-Teaser)
There is a wire, whose length is 10 feet longer than the circumference of the earth at the equator. The wire is formed into a circle, slipped over the earth, and placed at the equator. Assume the equator is also circular and smooth (no mountains or oceans). Can you fit your finger between the wire and the earth?
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1989 3.2 Carrera coupe; 1988 Westy Vanagon, Zetec; 1986 E28 M30; 1994 W124; 2004 S211 What? Uh . . . “he” and “him”? |
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01-17-2011, 06:44 PM
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ok, what's the trick?
how cold is it? what kinda "circle" - the kind with left over wire? what kinda "Earth" - the kind with flat poles? slightly pear shaped? wire orientation re part 1? Last edited by RWebb; 01-17-2011 at 07:02 PM.. |
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01-17-2011, 07:00 PM
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Don't be a woolly-minded liberal.
There is no thermal expansion or contraction. The wire is joined end to end. If I meant a circlip or a split ring, I would have said so. The equator is circular and the wire is placed over the equator.
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1989 3.2 Carrera coupe; 1988 Westy Vanagon, Zetec; 1986 E28 M30; 1994 W124; 2004 S211 What? Uh . . . “he” and “him”? |
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01-17-2011, 07:08 PM
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ok, then "No" - because I am too far away from it to reach mah fanger ovah theah
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01-17-2011, 07:18 PM
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Almost Banned Once
Join Date: Feb 2009
Location: Adelaide South Australia
Posts: 38,331
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Quote:
(Standing proud of the Earth by half it's thickness)
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- Peter |
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01-17-2011, 07:21 PM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
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yes. if there is ten feet of slack you should be able to pull it up nearly 5 feet at a single point. giving you more than enough space to stick your finger under it.
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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01-17-2011, 08:38 PM
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Ok guys, play it straight. As stated, the wire is a circle, the earth's equator is a circle. No stretching, deforming, digging a hole in the earth, etc. This is a test of your sense of geometry and scale, not your ability to invent loopholes :-)
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01-17-2011, 08:50 PM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
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then, there is no way.
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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01-17-2011, 08:56 PM
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Quote:
but then.. if it is too thin, it'd just cut right thru your finger... |
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01-17-2011, 09:02 PM
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Cogito Ergo Sum
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This is a bunch of BS.....
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01-17-2011, 09:09 PM
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Location: SF Bay Area
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No because of pi?
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01-17-2011, 09:49 PM
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durn for'ner
Join Date: Feb 2005
Location: South of Sweden
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Easily. There will be approximately a 3 feet gap.
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Markus Resident Fluffer Carrera '85 |
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01-17-2011, 10:11 PM
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10/(2*pi) ft of gap?
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83 911SC Targa Everything I say is my personal opinion, and has nothing to do with my team. Last edited by Won; 01-17-2011 at 10:22 PM.. Reason: forgot the unit |
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01-17-2011, 10:19 PM
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Now in 993 land ...
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What he is saying is that there is a circle with the circumference of the earth and then there is another circle with the circumference of the earth +10 feet. If you put them concentric to one another, will you be able to fit your finger between the two circles ..
I just did the math - no intuition here. Let's see what you think ... G |
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01-17-2011, 10:19 PM
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Yes, you could.
This could be easily proven algebraically, but I'm too tipsy. The problem does not state that the wire has the be evenly gapped around the earth (which is assumed)- if this were the case, no way. But if the wire was zero mass and zero thickness, it could easily be pulled taught until all the slack was in once place, and the wire met, with 5 feet of slack overlapping for a total of 10 feet of slack. Plenty of room for a finger.
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01-17-2011, 10:30 PM
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Quote:
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01-17-2011, 10:31 PM
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Now in 993 land ...
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Quote:
 G |
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01-17-2011, 10:34 PM
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eeh, When I think of 'wire' I think something that can be bent around. If it has to stay a circle, why not just call it a circle? Oh, I see, it's part of the sensory intuition of the problem...
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01-17-2011, 10:38 PM
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Location: Fresno, CA
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there's lots of slack on a ski lift cable. But you won't catch me putting my finger under it.
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01-17-2011, 10:44 PM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,189
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with no intuition and no exact math (just reason)... if you split the wire (wrapped tightly around) in two halves (180° apart) then splice in a couple five foot Sections, much of the wire would be a couple feet off the surface. ...Now imagine splicing in that 10' section in quarters,... spliced in at 90° apart. . those original arcs are pushed off more than a finger.
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Everyone you meet knows something you don't. - - - and a whole bunch of crap that is wrong. Disclaimer: the above was 2¢ worth. More information is available as my professional opinion, which is provided for an exorbitant fee. 
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01-17-2011, 11:13 PM
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1989 Porsche 911 Carrera 3.2
1986 Porsche 944 2.5l
