ilovephysics.com :: free online physics help, tutorials, forums, classes, misconceptions in / Rope problem

JackMurd · 2006-07-29 01:18:11

Let's say I have a rope ( line, cable, fishing line, whatever...). We know its tensile strength. For our purposes, the tensile strength will be the breaking strength and there is zero uncertainty. Let us say: 20 pounds. It will hold twenty pounds. It will break at 20.00001 ( etc.) pounds. To keep things simple, the rope will not stretch.

First question: If the rope itself weighs 0.1 pound per foot, then 200 feet will weigh 20 pounds. Will a greater than 200 foot length of rope, hanging vertically, support itself, or will it break of its own weight? If so, why? If not, why not?

JackMurd · 2006-08-02 08:06:24

I am disappointed that I received no reponses on this problem.

BenTheMan · 2006-08-04 21:34:27

The obvious answer is that the rope should break near the top, but I'm guessing there's some catch or something...

The way I would think about it is a small length of the rope supporting a point mass consisting of the rest of the rope. Is this some sort of trick problem?

And I'm disappointed by your use of customary units.

JackMurd · 2006-08-06 04:32:08

Thanks for responding.

No, this is not some sort of trick problem.

Careful analysis of the problem as written will lead to the correct answer.

BTW, there is nothing wrong with using 'customary' units. Whether in pounds per foot or kilonewtons per millimeter, the units chosen are in no way material to the solution of a thought problem. I am disappointed that you are disappointed. LOL There are still a few of us around who prefer legacy units over the metric system.

________

Don't try to teach a pig to sing. It wastes your time and annoys the pig.

Anon.

Announcement

#1 2006-07-29 01:18:11

Rope problem

#2 2006-08-02 08:06:24

Re: Rope problem

#3 2006-08-04 21:34:27

Re: Rope problem

#4 2006-08-06 04:32:08

Re: Rope problem

Board footer