Tension in Wire: Free Body Diagram & Calculation

[St@rbury]

forces quiz help please!

Homework Statement

the distance between two telephone poles is 50.0m when a 1.00kg bird lands on the telpephon wire midway between the poles, the wire sags .200 m. draw a FBD of the bird. How much tension does the bird produce in the wire? ignore the weight of the wire.

Homework Equations

f=,uN

The Attempt at a Solution

I got the free body diagram. but they don't give you any angles, so when i I am not sure how to proceed?

 

[qspeechc]

Well, you need to assume the poles are of the same height. Now the bird is mid-way between the poles. This is important. With that information, what can you say about the tension in the wires that go from the bird to the poles? In what ratio are they? Then you can draw your FBD, and solve it how you like, by resolving the forces, or with a triangle of forces.

 

[St@rbury]

the tensions would be equal, so then i set up the triangles, but i can't use sin or cos because i don't have an angle

 

[qspeechc]

You do have an angle. The distance between the poles is 50m and the line sags 0.2m, you can get an angle from that information.

 

[St@rbury]

o0o right...i could do inverse tan and that would give me the angle