## Welcome to BrainDen.com - Brain Teasers Forum

 Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account. As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends. Of course, you can also enjoy our collection of amazing optical illusions and cool math games. If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top. If you have a website, we would appreciate a little link to BrainDen. Thanks and enjoy the Den :-)
Guest Message by DevFuse

# Wired Equator

67 replies to this topic

### #41 DechWerks

DechWerks

Newbie

• Members
• 5 posts

Posted 04 December 2007 - 12:03 PM

To add to schmiggen's viable alternatives, without doing math, why not simply dig a hole where said string along the great circle matches said perfectly spherical planet and crawl under?

Nice math for the win though.
• 0

### #42 pastry

pastry

Newbie

• Members
• 1 posts

Posted 08 January 2008 - 06:34 AM

Easily.
It never said that it was wrapped around the world, just that it was 10 meters longer than the circumference.
• 0

### #43 Quinten27

Quinten27

Newbie

• Members
• 10 posts

Posted 11 January 2008 - 02:10 AM

Easily.
It never said that it was wrapped around the world, just that it was 10 meters longer than the circumference.

Maybe I'm a bit off on my thinking here, but it seems that would be plenty of room for even a small car to pass through. Wrap the wire around the earth, place two stakes in the ground a meter or so away from each other and pin the wire to ground at those two points, with the extra 10 M of slack between the two stakes. You now have a 1 meter gap in which the wire can be raised (use tent poles or hook to a tree branch to hold in place) atleast 4 meters off the ground (4 meters up, 1 meter over, and another 4 meters back down to the other stake, with an over an extra meter to spare). This would leave plenty of room to move under the wire. The question never says the wire is distributed evenly across the surface of the earth.

The other option would be to dig a hold underneath it, cross under the wire where it runs over a canyon, or possibly swim under it when it crosses the ocean or a lake.
• 0

### #44 GeoTeter

GeoTeter

Newbie

• Members
• 1 posts

Posted 17 February 2008 - 06:47 AM

Earth is not a smooth surface by any standards.

But still, those feel like cheating answers somehow.

Actually, it is. If you were to view the Earth on the same scale as, say, a billiard (pool) ball, its actually smoother than the ball!

Everything depends on your frame of reference.
• 0

### #45 recarv

recarv

Newbie

• Members
• 1 posts

Posted 17 February 2008 - 03:27 PM

The answer trail to this reads like the Monty Python skit where they try to determine whether or not a woman is a witch!

This question is ambiguous from the start -"world is approximately 40000km?" This leaves room for the flea immediately.

But lets for a minute assume that we're talking about a perfect sphere, which some people have taken for granted and started in on the geometry principles....

Unfortunately given the wording of the question, the geometric principle only is worth using if you're assuming the 10m (about 33 feet) of extra cable is distributed evenly to make another ever so slightly larger perfect circle around the 40000km circle.

However, it doesn't say in the question that this must be so, so I'm assuming you can use all 10m (about 33 feet of slack) the slack to produce a deformity at one point in the sphere large enough to fit all thre contestents through. At the theoretical limit you could make an area 5m (15feet or so) high (you need the other 5m to complete the other half of the arc deformity) that has almost no width. At this point we should consider the width of the person...see why this question is dumb? Some simple integral calculus could provide you with the area beneath the arc deformity which would give you a better idea of the continuous space underneath through which the contestants would have to fit...but again to perform the integral we'd need the question to have provided a function to describe the arc.

Now, some practical implications of this might involve the tinsel strength of the wire, its pliability in forming the small arc deformity. The mass of the wire and strength required to cause the deformity, etc...but all this could fall into the "approximately" area that makes this question inherently confusing.

I think the question should be worded more clearly.
• 0

### #46 rookie1ja

rookie1ja

Senior Member

• Site Admin
• 1341 posts
• Gender:Male
• Location:Slovakia

Posted 17 February 2008 - 04:37 PM

to recary:
word it
• 0

rookie1ja (site admin)
Optical Illusions
Support BrainDen

"To start: Press any key... Where's the 'any' key?" - Homer Simpson

### #47 tesseract

tesseract

Newbie

• Members
• 1 posts

Posted 21 February 2008 - 10:32 PM

I enjoyed this problem... it seems to defy logic. I did the math again for myself, but it is still hard to believe adding only 10 meters to the wire would evenly lift it more than five feet from the surface of the "earth" sphere. Thanks.
• 0

### #48 Lost in space

Lost in space

Senior Member

• Members
• 4009 posts

Posted 21 February 2008 - 10:48 PM

Quick thought - 10m extra will form an "opening" 3.333r x 3.333r x 3.333r if you use it only one place on the equator, assuming the equator is were it is meant to gbe applied.

Sorry if this is a duplicate -too many answers to go through!
• 0

### #49 Sharpshark

Sharpshark

Junior Member

• Members
• 21 posts

Posted 26 February 2008 - 01:27 AM

Depends. THe Wire at the time of measurement might be smaller than its size when it expands from the suns heat. Otherwise, no none of them could because it would be 10/40000 meters wide.
• 0

### #50 Ciahra

Ciahra

Newbie

• Members
• 4 posts

Posted 28 February 2008 - 07:17 AM

wow. you guys are thinking way too much on this one. no math is necessary. no geometry. look at it this way...

a sphere, perfect in nature, made of metal so as not to be cut, precisely 40k meters in circumference and with standard gravity (for you geeks out there...)

if a wire with a length of 40010 meters is stretched out in an equatorial line around the sphere, when the sphere is enveloped (along that line) there will be 10 meters in abundance. those 10 meters can be manipulated in such a way that many large things could pass under the wire, as the space created could, for example, be 4 meters high and 2 meters wide. now you can do the math.

using equations that involve circumference, diameter, and radius assume the wire would be equidistant from the sphere at all points around that sphere. such conditions were not given in the puzzle, so should not be inferred.
• 0

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users