Thursday, May 10, 2007

The Rope Question

A long time back a friend had posed this question:

"You have a tennis ball and the earth. You have two ropes. 

One rope ties the tennis ball along its surface. It fits exactly.

The other rope does the same to the earth,

i.e. exactly covers the circumference of the earth.

You now increase the length of each rope by 1 inch.

Form a circle with each rope covering the tennis ball and the earth

Is the distance between the tennis ball and its new circle greater
than that between the earth and its new circle?"

She was looking for the logic and not the Math.

Now since neither my logic nor my Math skills are anything to talk home about, I turned to someone who might have done justice to the problem.

This is the answer I got back:

"Is this a trick question?

If it were, I would ask,

1) What kind of a rope was used, i.e. what was the modulus of elasticity? Did you twist the rope during the process?

2) What was the tension in the rope while it was stretched?

3) What were the temperatures during the experiments?

4) What is the coefficient of thermal expansion, in case there was a temperature variation?

5) How fast was the measurement done? (may become important if we are thinking in speeds near that of the light)

6) The question that has always haunted me since can you tie a knot (to add that 1 inch) without altering the original length?

(That will be close to Heisenberg’s heart too.)

7) Question 6 alone can generate a whole set of debate, like how tight was the knot?

( I won't even get into the uncertainty in measurements!)

8) If you asked my Graduate school advisor he'd ask, "Did you repeat the experiment?"

9) My present boss would ask: "Did you write that up?"

(Just in case you didn't know what writing up is all about, it refers to writing up a US patent)

10) And his boss would suggest," Sign an NDA (non disclosure agreement) before you answer the question!"

11) The Corporate VP would ask, "Can we get the problem solved in China?"

12) Tom Skilling would ask, "Was there a Jet stream in the upper atmosphere pushing the rope?"

13) Dubya Bush would say " Are you sure it is not an act of terrorism?"

14) My Dad who loves a gourmet meal and is a secret poet at heart would ask, " May I hope, to eat the rope?"

15) My health freak brother would say, " Jump the rope 20 min a day to get rid of the extra calories."

16) My sister who is always looking for an excuse to scold me will say, " Who asked you to get in to such a mess with ropes!"

17) My Mom who spent her entire trip to the US trying to find a way to wash and dry her sarees would ask, "Can we dry our laundry on that rope?"

18) And last, my wife who is forever trying to stock up on things will say, " Can we have another rope? Then we can do the experiment with one and keep the other in stock just in case we need it later."

Thanks for asking. Hopefully I answered your question."

Needless to say I was left speechless.

*I'd like to thank AB for the question and AR for sending me the reply.

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Blogger Dreamcatcher said...

Wow :)

3:08 PM  
Blogger twip said...

Goes to show that you can completely prevent the pointless questions by drowning the 'asker' in pointless counter-questions.

Hmm. I must try this out sometime. Heh.

3:58 PM  
Blogger Prerona said...

lol. interesting puzzle!

4:21 PM  
Blogger Unknown said...

lol @ t-w-i-p.

my answer to the original question would be No.

But AR's response kicks ass. :p

7:42 PM  
Blogger Sudipta Chatterjee said...

Ha hahaaa.... and a grad student would ask, "Is there some funding on the extra inch of the rope?" :D

9:41 PM  
Blogger Artnavy said...

LOL- fitting retort

12:52 AM  
Blogger Bong Mom said...

Ha, ha, ha :) :)

1:59 PM  
Blogger Eroteme said...

This was hilarious!! Thanks a tonne for sharing this. I am sure if someone asked Arundhati Roy (I hope that isn't what AR stands for) she would say that this is it is typical of the Empire to think of the world as a larger tennis ball!

12:34 AM  
Blogger Rohini said...

Er..I lost you at modulus...

6:13 AM  
Anonymous Anonymous said...

Seriously?! :D:D:D

12:33 PM  
Blogger Eroteme said...

Oh! BTW, I think the answer would be No.

12:01 PM  
Blogger Bharath Hemachandran said...

Sounds like something asked in an interview :)

Nice answers though. I do ask quite a few of these back when I am asked such questions.

Of course never mind the amount of money and resources that would be wasted in trying to drag a monster rope to circle the earth correctly!

10:15 AM  
Blogger Cee Kay said...

Ummmm... I think the answer would be 'Yes'.

11:35 AM  
Blogger Adarsh A. Varghese said...

whew! good one!

1:34 PM  
Blogger Little Miss Muffet said...


1:38 PM  
Blogger M (tread softly upon) said...

@ all thanks for stopping by.

11:40 AM  
Blogger Prometheus_Unbound said...

This sounds like the gr8 Indian rope trick. Hmmmm, now I am going to loose sleep all night trying to work this one out or trying to add a few questions to your lisl. :D

3:21 AM  
Blogger Wanderlust said...

hmmmm....i may sound stupid...among all the great writers here...but this post has actually gone over my head like a tangent :p

12:32 PM  
Anonymous Anonymous said...

I was actually asked this question in an interview about 8 months ago and was totally stumped. It was for a programmers job and I wondered what the circumference of a ball and the earth had to do with writing software. The interviewer proceeded to write each step on the white board to prove that the distance would be the same for both the ball and the earth. Fascinating! Needless to say I haven’t heard anything about the position and they're still advertising the same job 8 months later.

7:30 PM  

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