# Homework Help: Caternary Problem

1. Feb 22, 2014

1. The problem statement, all variables and given/known data
In most problems in this book, the ropes, cords, or cables have so little mass compared to other objects in the problem that you can safely ignore their mass. But if the rope is the only object in the problem, then clearly you cannot ignore its mass. For example, suppose we have a clothesline attached to two poles (Fig 5.61). The clothesline has a mass $M$ and each end makes an angle $\theta$ with the horizontal. What are (a) the tension at the ends of the clothesline and (b) the tension at the lowest point? (c) Why can't we have $\theta=0$? (d) blahblahblah [For a more advanced treatment of this curve, see K.R. Symon, Mechanics, 3rd Ed)

2. Relevant equations

Newton's Laws

3. The attempt at a solution
Unfortunately, I have absolutely no experience with problems such as this. My work is here (look at the second attempt, the first one was garbage): http://s15.postimg.org/xoou3zhh7/IMG_0743.jpg [Broken] , and I am pretty sure I have the wrong answer; if I feel like it's too easy I'm definitely doing it wrong.

Last edited by a moderator: May 6, 2017
2. Feb 22, 2014

### Saitama

The tension acts along the rope, not horizontally. You only need to show mg at the centre of rope. Can you proceed now?

Last edited by a moderator: May 6, 2017
3. Feb 22, 2014

Doesn't the tension (on one end) need to support only half of the rope?

4. Feb 22, 2014

### Saitama

Nope but its component would do. ;)

5. Feb 22, 2014

Got the answer I was looking for. Thanks for the help!

6. Feb 22, 2014

### tiny-tim

nice

btw, it's catenary

(from the latin "catena" meaning "chain", cf. concatenation)

7. Feb 22, 2014