What Does Feynman Mean by the Heat Energy in Springs?

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Discussion Overview

The discussion centers around Richard Feynman's explanation of heat energy in springs, particularly focusing on the atomic behavior within springs during energy conversion processes. Participants explore the implications of atomic movement, energy conversion from kinetic to heat energy, and the mechanics of potential energy in springs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks clarification on Feynman's statement regarding atomic arrangement in springs and the absence of "jiggling" during energy transfer.
  • Another participant argues that without atomic jiggling, there would be no conversion of kinetic energy into random kinetic energy, suggesting that energy conversion is essential for heat development.
  • A participant posits that when a spring is stretched and released, the conversion of kinetic energy occurs as atoms move randomly rather than simply stretching and contracting.
  • There is a discussion about why the focus is on the conversion of kinetic energy to heat energy, despite the presence of both potential and kinetic energy in a spring.
  • One participant suggests that potential energy could be converted directly to heat under specific conditions, such as a compressed spring rusting away.
  • Another participant clarifies that atoms in a spring do not stretch and contract but shift relative to one another, contributing to energy loss through random movements.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms of energy conversion in springs, particularly regarding the roles of atomic movement and the relationship between potential and kinetic energy. No consensus is reached on these points.

Contextual Notes

Participants discuss various assumptions about atomic behavior and energy conversion processes without resolving the complexities involved in these interactions. The discussion reflects a range of interpretations of Feynman's ideas.

Aleoa
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In an ideal reversible case, a spring is a simple perpetual machine ; in order to introduce the slowdown of a spring in a real case and the consequent heat development in the spring, Feynman writes (here par. 4.4):

"Inside a spring or a lever there are crystals which are made up of lots of atoms,
and with great care and delicacy in the arrangement of the parts one can try to
adjust things so that as something rolls on something else, none of the atoms do
any jiggling at all"

I don't understand what Feynman means with this sentence. Can you help me ?
 
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If there were no jiggling, there would be no conversion of kinetic energy of the rolling object into random kinetic energy in that object and/or in the something else it is rolling on. In a spring this would not be rolling but e.g. wringing.
 
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BvU said:
If there were no jiggling, there would be no conversion of kinetic energy of the rolling object into random kinetic energy in that object and/or in the something else it is rolling on. In a spring this would not be rolling but e.g. wringing.

Suppose we stretch and the release a spring with no weight connected. If I've understood correctly, the conversion of kinetic energy is due to the atoms that, instead of stretching and contracting, start to move in random ways . Am i correct ?

ps: since in a spring there is both potential energy and kinect energy, why do we speak only about "conversion of kinetic energy into heat energy " ?
 
Aleoa said:
ps: since in a spring there is both potential energy and kinect energy, why do we speak only about "conversion of kinetic energy into heat energy " ?
When potential energy is converted to heat in a spring, it is usually first converted to kinetic energy.

I suppose that one could convert potential energy directly to heat if a compressed steel spring rusted away to nothing without breaking first.
 
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jbriggs444 said:
I suppose that one could convert potential energy directly to heat if a compressed steel spring rusted away to nothing without breaking first.
Interesting thought. I guess anything that would reduce the spring constant while it was extended would also work.
 
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Aleoa said:
Suppose we stretch and the release a spring with no weight connected. If I've understood correctly, the conversion of kinetic energy is due to the atoms that, instead of stretching and contracting, start to move in random ways . Am i correct ?
 
The atoms do not stretch and contract. They shift relative to one another. But they do not shift simultaneously and smoothly as a continuous whole. So yes. In addition to the bulk shift of position, there is energy lost into random wiggles.
 
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