Length of wire with given yielding strength

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Discussion Overview

The discussion revolves around determining the maximum length of a steel wire that can be suspended from a high-altitude balloon without yielding, given a yielding strength of 40 ksi. The scope includes homework-related problem-solving and mathematical reasoning involving stress and strain concepts.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • The initial poster expresses uncertainty about how to calculate the maximum length of the wire and mentions relevant stress and strain equations.
  • One participant suggests calculating the volume of the wire and subsequently its weight, implying that the wire's weight must be considered in relation to the buoyancy force of the balloon.
  • Another participant points out the lack of diameter information, which is necessary for calculating the volume of the wire.
  • A suggestion is made to let the diameter be a variable (d) to facilitate calculations, with the expectation that it may cancel out in the final solution.
  • There is a confirmation that the weight of the wire is equal to the buoyancy force created by the balloon.

Areas of Agreement / Disagreement

Participants generally agree on the need to consider the wire's weight and buoyancy forces, but there is no consensus on how to proceed with the calculations due to the missing diameter information.

Contextual Notes

The discussion highlights limitations related to the absence of the wire's diameter, which affects the ability to compute volume and weight accurately. There are unresolved mathematical steps regarding how to incorporate these variables into the problem.

Who May Find This Useful

This discussion may be useful for students or individuals interested in mechanics, material science, or those tackling similar physics homework problems involving stress, strain, and buoyancy concepts.

megr_ftw
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Homework Statement


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??


Homework 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)

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
 
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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?
 
they don't give you the diameter so you can't calculate the volume
 
Could you let the diameter be d?
 
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?
 
Yes, you could say that. Well said.
 

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