rope around the world

The UN have decided to put a rope going round the equator of the Earth. They are presuming that the Earths circumferance is 40 000 km and that there are no mountains in the way.
Someone told them that people are going to trip over this rope, so the UN have decided to have the rope hanging at a constant distance of 10m above the Earths surface (Russians named Vladaskova on stilts hold the rope up). How long does the rope have to be now.

and for bonus points, lets say Vladaskovas would have to be placed every 5m along the rope, how many stilts would be needed?

Well, lets use 39350 / pi = 12525.

Add .020 = 12525.514 now multiply by pi. So..

39350.063 km of rope. 63 extra meters of rope.

I think you forgot your units there. Just looking at your answer I saw it was totally ridiculous.

oh BTW, no offense, hehe;)

I am too lazy to figure it out but the mistake that ^^^^ made is that he thought that number was diameter not circumference. it really is circumference

origional length = 2*Pi*r = circumference = 40000km

new radius = r+10
=> new length = 2*Pi*(r+10)
= 2*Pi*r + 2*Pi*10
= old value + 2*Pi*10
=> extra length needed = 20*3.1415... = 63m

nothing wrong, not ridiculous, just unobvious :p

And as for the second one: (40,000 + 20pi)/5 = 8,000 + 4pi guys holding the rope up :)

Yeah, except:

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how many stilts would be needed

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assuming ppl need two stilts each (u never know, some might be clever and stand on one leg, some might need three)
then (8,000 + 4Pi)* 2 = 16,000 + 8 * Pi stilts are needed

At every 5m, (and we really should be doing this every 15feet)
have we taken into account sag on the rope? What is the thickness of the
rope and how much force is being exerted to pull it taught?

Well, if you really want to try this, lets say the rope is 5cm thick. The force on it would be g. I'm pretty sure that you can ignore g becoming smaller as the distance from the earths centre increases as it only 10m. I have no idea why or how you would want to do this, but if you really want to, there you go.

well actually, I was being funny, but
at 40 000km it seems like it would be important since you won't be able to hold the rope in a perfect circle.

The next question is: How did you get the UN to agree on anything?

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The next question is: How did you get the UN to agree on anything?

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Hehehe, I knew something like that would be coming eventually, it only was a matter of time.

At least they finally did agree on something important :rolleyes:

:D

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Originally posted by jemidiah
At least they finally did agree on something important :rolleyes:

:D

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And, thankfully, the US didn't veto the decision for once.

For the first part of the problem, the circumference does not matter. The rope must have a diameter 20 meters more than the circumference of the Earth. The circuference of a circular rope 20 meters more in diameter is 20Pi = 62.831 853 meters.

Rope = 40,000,062.831 853 meters.

Divide by 5 results in 8,000,012.566 men holding the rope. Multiply by the number or stilts per man. Looks like 16,000,025 men to me.