Conservation (momentum and ke)

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Discussion Overview

The discussion centers on the conservation of momentum and kinetic energy during perfectly elastic collisions between atoms. It explores the definitions and implications of these concepts in the context of atomic interactions.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asserts that both momentum and kinetic energy are conserved in a perfectly elastic collision, referencing the definition of such collisions.
  • Another participant suggests that while kinetic energy is not conserved throughout the collision process, it is equivalent at the initial and final states when the particles are not interacting.
  • A further contribution indicates that total energy is conserved throughout the collision, implying a distinction between kinetic energy and total energy conservation.
  • One participant describes the mechanism of energy transfer during the collision, suggesting that kinetic energy is temporarily stored in a repulsive field and then returned to the atoms as kinetic energy, drawing a parallel to mass-spring oscillators.

Areas of Agreement / Disagreement

Participants express differing views on the conservation of kinetic energy during the collision process, indicating that there is no consensus on this aspect. The discussion remains unresolved regarding the nuances of energy conservation in elastic collisions.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about energy conservation and the definitions of elastic collisions, which may depend on specific interpretations or conditions.

Infrasound
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When two atoms collide, and no bonding takes place, i.e. a perfectly elastic collision, would both momentum and kinetic energy be conserved?
 
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Infrasound said:
i.e. a perfectly elastic collision
Well, yes. That's the definition of an elastic collision.
 
The kinetic energy is not conserved throughout the process like the momentum, but it is the same at t=-infinity and t=infinity if the two particles are not interacting at those "moments" (i.e. long before and long after the collision).

The total energy is conserved throughout the collision, though.
 
In between the end points (but most especially right around the collision) the kinetic energy is transferred the the repulsive field pushing the atoms apart. This field momentarily stores the energy and then by pushing on the atoms, the energy is delivered back as kinetic again.

This is also what happens in a mass-spring oscillator.
 

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