# Length of wire with given yielding strength

1. Jan 20, 2010

### megr_ftw

1. The problem statement, all variables and given/known data
A steel wire is being hung from a high altitude balloon. What is the greatest length is can have without yielding if the steel yields at 40 ksi??

2. Relevant equations
I know all the stress and strain equations but I have yet to find or be taught an equation for finding this. I feel like it's very simple but I just can't figure is out. Stress= force/area
Stress= (E-modulus)(strain)

3. The attempt at a solution
The answer is 11,800 ft or m, not sure which one. But I have no clue how to get to the answer. I did my homework and everything but this problem was "recommended" and I NEED to figure it out
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 20, 2010

### nvn

megr_ftw: Hint: Wouldn't you want to compute the volume of the wire, and then the weight of the wire? Wouldn't the wire be carrying that weight?

3. Jan 20, 2010

### megr_ftw

they dont give you the diameter so you cant calculate the volume

4. Jan 20, 2010

### nvn

Could you let the diameter be d?

5. Jan 20, 2010

### megr_ftw

oh yea i guess that would be the easiest option. as long as it cancels in the end.

The force of the wire's weight equals the buoyancy force created by the balloon right?

6. Jan 21, 2010

### nvn

Yes, you could say that. Well said.