Tension in a wire, length change

  • Thread starter CINA
  • Start date
  • #1
60
0

Homework Statement



3. A flying chicken (m = 450[gram]) lands in the middle of a taught laundry wire of length l=10[m]. The wire has a negligible mass. The chicken causes the wire to stretch by 0.05% from its original length. Find the tension in each segment of the wire.

http://img517.imageshack.us/img517/2922/asdfgggea7.th.jpg [Broken]http://g.imageshack.us/thpix.php [Broken]


Homework Equations



Fext = 0

X) Ft1x - Ft2x = 0

Y) Ft1y + Ft2y - Fg = 0


The Attempt at a Solution



Since the length increases by .05% you can make a triangle with lengths 10m ( the origianl length), 5.25m and 5.25m (half of the new length with the chicken in the middle). you can split this into two right triangles with sides 5-5.25-x (doesn't matter right?). Using arccos (5/5.25) you get 17.8 degrees.

Fty1 & Fty2 = Ftx tan 17.8

getting 2 Ftx tan 17.8 = Fg

Ftx = 6.87 N

Ft = Ftx/Cos 17.8 = 7.2 N

The Problem

Students in my class got 69.8 N, and after looking up tension I found that it increases as things stretch. Our teacher never said anything about this (but gave a problem on it). How does the streching of the string play into this? Is there some equation I'm not putting to use?
 
Last edited by a moderator:

Answers and Replies

  • #2
325
0
7.2 N looks fine to me. I doubt the stretching of the string has anything to do with it other than giving you the triangles.

Just by looking at it I would say the other students in your class have done something wrong because of the size of their answer. It would give them about 21N upwards force, much greater than the mass of the bird.
 

Related Threads on Tension in a wire, length change

  • Last Post
Replies
2
Views
7K
Replies
5
Views
1K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
1
Views
921
  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
6
Views
5K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
5
Views
2K
Top