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Mechanics

Anant Kumar's Avatar
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Joined: 10 Jul 2008
Post: 598
22 Nov 2008 06:57:48 IST
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Four snails.
None

Four snails travel in uniform, rectilinear motion on a very large plane surface. The directions of their paths are random, (but not parallel, i.e.any two snails can meet), but no more than two snail paths can cross at any one point. Five of the (4 X 3)/2 = 6 possible encounters have already occured. Can we state with certainity tha the sixth encounter will also occur?


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Avirup Dasgupta's Avatar

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Joined: 30 Jul 2007
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22 Nov 2008 19:47:20 IST
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Sir,


  this is not a rigorous proof ---- just intuition.


Correct me if I'm wrong.

Anant Kumar's Avatar

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22 Nov 2008 21:46:43 IST
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Well your intution guided you wrongly.. obviously now you know the answer.. why don't you try it once more?

Soumik's Avatar

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Joined: 31 Jul 2008
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24 Jan 2009 19:06:33 IST
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Kaymant sir, I think I've finally got it....

We know 5 encounters have already occured, so any snail suppose be X has met 3 of his friends ----say P,Q,R.....

Now in my reference frame, X is at the origin....

P,Q,R thus have crossed the origin, For the remaining 2 encounters, P have met both Q & R.

Which further signifies that P,Q,R are moving in a st.line, thus the other 2.....Q&R must also meet each other at some other time.....thus 6 encounters is a must......

PLZ CORRECT & GIVE THE FULL SOLN IF I'M WRONG!

Soumik's Avatar

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24 Jan 2009 22:49:39 IST
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What happened, plz reply, is this right or wrong?

Anant Kumar's Avatar

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Joined: 10 Jul 2008
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24 Jan 2009 22:56:17 IST
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Yes, thats correct..




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