Rubber Bands and Energy Dissipation

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Discussion Overview

The discussion revolves around the energy dissipation in rubber bands when they are stretched and subsequently held against a surface, specifically exploring the conversion of mechanical energy into heat. Participants examine the extent of this energy loss and its implications, touching upon thermodynamic properties and experimental observations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that when a rubber band is stretched and then held against the lips, it feels hot, suggesting that energy is converted into heat.
  • Another participant questions the magnitude of this energy conversion, asking if a significant portion (e.g., 1 lb out of 10 lbs of force) is transformed into heat or if it is negligible.
  • Several participants share links to external resources related to the thermodynamics of rubber bands, although there are issues with accessing these links.
  • One participant describes an experiment where stretching a rubber band while heating it with a hair dryer results in a decrease in length, which contrasts with the behavior of most materials when heated.
  • A participant seeks to quantify the energy loss during stretching, asking for a percentage of energy converted to heat, while acknowledging that it may depend on experimental conditions.
  • Another participant clarifies that energy, not force, is being converted to heat and discusses the ideal conditions under which heat loss could be minimized.
  • It is mentioned that heat loss is influenced by factors such as thermal conductivity and emissivity, and that real processes differ from idealized models.

Areas of Agreement / Disagreement

Participants express varying views on the extent of energy dissipation in rubber bands, with no consensus reached on specific percentages or definitive conclusions regarding the energy conversion process.

Contextual Notes

Participants acknowledge that the energy loss may depend on experimental conditions and the definitions of ideal versus real rubber band behavior, but do not resolve these complexities.

pallidin
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Greetings all...

When I pull a fairly good size/quality rubber band and then quickly hold it against my lips, I feel it to be quite hot.
I assume that some of the energy used in stretching the rubber band is converted into heat by virtue of the properties of a "rubber band"

My question is this: Is this energy "loss" appreciable? That is(speaking hypothetically), if I pull with 10 lbs of force, is 1 pound of force converted into heat? Or is this conversion a real but "negligible" factor(much less than 1-lb in my hypothetical scenario)

Thank you.
 
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http://www.fofweb.com/Onfiles/SEOF/Science_Experiments/5-39.pdf#search='thermodynamics%20of%20a%20rubber%20band'

"[URL

pp.12-14

Edit links --- OK, now the stinkin' linkin' is workin'.
 
Last edited by a moderator:
Thanks for your response, but links are not working for me. Maybe something on my end.
 
Google "thermodynamics of a rubber band" and look at items 1 and 14. They're both PDF files, and for who knows what reason that's a function of my versions of Windows and IE, my ISP's software, and PF software, PDF links won't parse, and "insert link" doesn't seem to have done the trick --- you got "cannot display page" I presume?
 
Bystander said:
Google "thermodynamics of a rubber band" and look at items 1 and 14. They're both PDF files, and for who knows what reason that's a function of my versions of Windows and IE, my ISP's software, and PF software, PDF links won't parse, and "insert link" doesn't seem to have done the trick --- you got "cannot display page" I presume?

Yes, I am getting a "cannot display page". I will take your advise and do the Google seach as you stated. Thanks.
 
"A related interesting property which makes a nice demonstration is to
stretch a rubber band with a weight and heat it with a hair dryer. The
length of the rubber band will decrease, unlike most materials which would
lengthen, I.e. expand, when heated."

From: http://www.Newton.dep.anl.gov/askasci/gen99/gen99976.htm
 
OK, I guess I'm asking this: With an event of "stretching" a rubber band, some amount of force is converted to radiated IR.
Is there a "percentile" qoutient? Is it 10%, 1%, .001%, etc...
Granted, it depends on the experiment. But surely there is some qualitative value with respect to this.
 
pallidin said:
OK, I guess I'm asking this: With an event of "stretching" a rubber band, some amount of force

Not "force," energy, the integral of force times displacement.

is converted to radiated IR.
Is there a "percentile" qoutient?

In principle, the heat loss from the rubber band can be restricted to zero; this is part of "the ideal rubber band." So, no.

Is it 10%, 1%, .001%, etc...
Granted, it depends on the experiment. But surely there is some qualitative value with respect to this.

Qualitative? Yes, the rubber band is going to lose heat to the environment at a rate determined by thermal conductivity of materials in contact with it, the emissivities of surroundings, and this all gets back to comparisons of idealized adiabatic processes with real processes --- you can approach ideality in this case with insulation and radiation shields. What you then observe is a rubber band, the temperature of which is a reproducible function of elongation.
 

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