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a new riddle

here's a nice one to your collection -

a man stands on top a cliff, 400 meter high. he has a rope 300 meter long, and there are two rings fixed in the cliff, one where he stands and the other at the middle (200 meters) . how can he climb down the cliff ?

there is (almost) no "aha factor", and the solutions is feasable without "tricks" like tying the rope so it releases on a pull or things like that. the solution is realistic enough to try yourself (that is, if you dare climb a rope down 400 meters...)

yoav morag
Monday, February 18, 2002

Here's a thought (although i'm not sure it'd work)

Tie a fairly heavy rock 100 meters into the rope (and thus 200 meters from the other end).
Thread the long side through the ring until the rock reaches the ring and holds it there, too big to go through the ring itself.
Climb down the 200 meters of rope to the second ring.  Let go of the rope and the rock (being heavy enough) pulls the long side of the rope through the top ring, thus bringing the entire rope down to you.

Of course this relies on you being able to catch a rope falling a fairly fast speed, but considering you're climb down a 400 meter cliff I figure you'd be agile enough to do that.

You can repeat the same process for the second ring so that you can retrieve the rope at the bottom of the cliff.
(or you can just tie it to the ring and leave the rope there)

Dave Schnizlein
Wednesday, February 20, 2002

The approximate minimum weight of the rock would be just over the weight of 100 meters of the rope.

Dave Schnizlein
Wednesday, February 20, 2002

Well here's a solution, if you are able to cut the rope...

Cut the rope into a 100 meter segment and a 200 meter segment.  Tie one end of the 100 meter segment to the top ring.  Tie the other end into a small loop.  Then thread the 200 meter segment through the loop in the 100 meter segment.  Tie the two ends of the 200 meter segment together, so that it forms a circle.  This forms 200 meters of rope which you can use to climb down to the second ring.  Once there, you can slide the 200 meter segment until the knot holding its two ends together reaches you.  At this point you can untie the knot, pull the rope through, and you have a 200 meter long piece of rope to use to climb to the ground, leaving a 100 meter segment hanging from the top ring.

Mike McNertney
Thursday, February 21, 2002

well actually what i had in mind is mike's solution. but the rock is kinda cute, too... i wonder what will happen if the rock falls on your head, tough.

yoav morag
Sunday, February 24, 2002

"but the rock is kinda cute, too"
'Cute', wonderful

And who can't catch a 50 pound rock falling at terminal velocity?

Dave Schnizlein
Sunday, February 24, 2002

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