- #1
Ryker
- 1,086
- 2
Homework Statement
A wire, weighing 10N, is put on two poles that are 40m apart. Due to its weight, the wire dips for 1m. What are the forces the wire exerts on each of the poles? The wire can be said to take a shape of an arc of a circle.
Homework Equations
The Attempt at a Solution
Well, the solution is said to be 50N and, to be honest, I did reach it, but the method seemed a bit brute. Therefore I'm just looking for a confirmation (or refutation, for that matter) on its validity, and even moreso, an alternative one for reaching the same result.
Basically what I did is I sketched a circle and calculated the angle under which the tangent would hit each of the poles. Because we had that triangle with the cathetis' lengths 1m and 20m, after some manipulation and use of rules on the similarity of triangles, I got to an angle of 2,86º. Then I drew the final triangle with one catheti being 5N - half of the wire's weight, since there are two poles - and just calculated the hypothenuse (tangent) using the cosine function.
So how does that sound? What I'm "worried" about is that this problem is from a book that we used in our first year of high school and, at least from what I remember, we used simpler maths to reach solutions then (by simpler I mean we probably didn't use that circle thing, but we did use trigonometric functions). So while I'm glad I got to the solution, I'm not sure I should've reached it this way (I'm not saying it's wrong if you can reach a certain solution your own way, but I would like to know the supposedly "proper" way, as well).
Any thoughts would be greatly appreciated.