Einstein's Equation: Energy Changes & Mass - What Happens?

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Discussion Overview

The discussion revolves around Einstein's equation "E = mc^2" and its implications regarding energy changes and mass in objects, particularly in the context of kinetic and potential energy transformations. Participants explore theoretical aspects of energy conservation, motion in a vacuum, and the relationship between energy and mass.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that an object losing energy results in a slight loss of mass, while gaining energy results in a slight increase in mass, questioning what happens to the kinetic energy when the object comes to rest.
  • Another participant argues that the equation applies to energy at rest and that an object's linear momentum does not change spontaneously, implying that energy loss must be accounted for through interactions with forces.
  • A question is posed about whether a particle with kinetic energy continues to move indefinitely in a vacuum or if it slows down as its kinetic energy is used up.
  • A later reply confirms that a particle in a vacuum will continue moving straight forward unless acted upon by an external force, referencing Newton's first law.
  • One participant seeks clarification on the relationship between kinetic energy and mass when a mass releases a photon, introducing the concept of momentum imparted by the photon affecting the mass's speed.

Areas of Agreement / Disagreement

Participants express differing views on the implications of energy changes on mass, the nature of motion in a vacuum, and the effects of energy loss. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

There are limitations in the assumptions made about energy transformations and the definitions of kinetic and potential energy. The discussion does not resolve the mathematical relationships involved in these transformations.

Omar
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According to Einstein’s equation “E = m c^2” an object that loses energy loses a VERY slight proportion of its mass. An object that, on the contrary, gains energy also gains a VERY slight increase in mass.

Now, if an object (in space, or vacuum, say) moves or changes position, in general physics we say; the potential energy of the object has transformed into kinetic energy (because the object has moved). Thus it goes that the object lost part of its mass (or potential energy) as kinetic energy, where has the lost part gone or transformed into? Remember the law of conservation of energy states that energy lost = energy gained.

Let me re-frame that: What happens to the K.E. after the object sets to rest? Is it re-transformed into potential energy so that the mass of the object returns the same?

NOTE: I know I'm bullsh*tting, but.. what to do?
 
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The equation quoted is for the energy at rest. If the particle moves, that's not true.

And remember, and object don't changes its linear momentum spontaneously, it does when something happens for example when a disipative force makes the object loose speed and this energy goes god knows where (internal work, heat, ...). So we can't imagine a isolated particle with a linear momentum p which spontaneusly reduces its speed and finally keeps in rest. Thats magic, not physics :)
 
So you're saying when a particle moves (in vacuum and without gravity or any other force applying on it) it will just keep on moving straight forward?

Let's say that a particle has a K.E. of 10 Joules; is this embodied by the continuous motion of the particle or does the the particle slows down as the K.E. is used up?
 
So you're saying when a particle moves (in vacuum and without gravity or any other force applying on it) it will just keep on moving straight forward?

That's precisely what will happen! (Newton's first law)

Cheerio!

Kane
 
Omar said:
Let me re-frame that: What happens to the K.E. after the object sets to rest? Is it re-transformed into potential energy so that the mass of the object returns the same?
I am not sure I understand your question. Are you asking how does the KE of the mass m that releases a photon change? If so, the answer lies in the momentum imparted by the photon to the mass. It imparts E/c momentum to the mass so the mass experiences a change in speed of v=E/mc
 

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