# Rope puzzle

Discussion in 'General Discussion' started by 2scoops0406, 18 Jan 2009.

1. ### 2scoops0406

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Here's another one but with far less safety implications (I may have lifted this from this forum so apologies if I have)

Assume the earth is a perfect sphere. You have a rope that stretches arounf the equator so the the ends of the rope just touch.

Now you want the same rope to be uniformly suspended 1 foot above the surface, how much extra rope do you need?

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3. ### blondini

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That ones as easy as pi

4. ### 2scoops0406

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If your saying it's pi feet, then I'm sorry, that's not correct.

5. ### 2scoops0406

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Well sorry about not being intuitive, the point is well made, in that I had to check the calculation a couple of times as I originally thought I'd made a mistake.

6. ### Softus

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The answer is (2 * pi) feet.

7. ### 2scoops0406

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Correct.

8. ### blondini

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I see my enlargement on my pie joke has been removed

9. ### 2scoops0406

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My fault, hijacked a post.

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11. ### peteftw

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sorry to get in a bit late on this one, are you saying the rope only has to be 6' longer?

12. ### tim west

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what if it's bungee rope?

13. ### blondini

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Close. Just two times the value of pi.

(1' extra radius = 2' extra circumference...)

14. ### Softus

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Huh?

15. ### blondini

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Uhuh.

16. ### Softus

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I beg to differ.

17. ### peteftw

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so what if it was round the circumferance of an elephants belly would it still need to be 6' longer to hover 1'?

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