What Happens When an Object on Earth Loses Mass Suddenly?

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Discussion Overview

The discussion revolves around the hypothetical scenario of an object on Earth suddenly losing a significant amount of mass. Participants explore the implications of this mass loss on the object's behavior, particularly whether it would rise or remain stationary, while considering the principles of physics involved.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that if an object loses mass suddenly, it might rise due to the release of potential energy, similar to a compressed spring expanding.
  • Others argue that if the mass of an object resting on the ground is reduced, the forces acting on it would also decrease, suggesting that the object would remain stationary.
  • A participant notes that there is no known mechanism for a spontaneous loss of mass, except in specific cases like radioactive decay.
  • One participant rephrases the scenario as a problem involving a cube of mass 2 tons and speculates on the effects of a sudden mass change to 1 kg, questioning the behavior of the surface beneath it.
  • Another participant emphasizes that the question, as posed, is inconsistent with classical physics, but suggests that an elastic material would decompress if the load on it were suddenly reduced.

Areas of Agreement / Disagreement

Participants express differing views on the outcome of a sudden mass loss, with no consensus reached. Some believe the object would rise, while others maintain it would not move. The feasibility of the scenario itself is also contested.

Contextual Notes

The discussion highlights limitations in the assumptions made about mass loss and its implications, as well as the dependence on definitions of physical laws. The scenario presented does not align with established physical principles.

RedLine
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Lets say a heavy object was resting on Earth and suddently it lost allot of mass.
Will the object go up? (The loss of mass happened instantly )
 
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RedLine said:
Will the object go up? (The loss of mass happened instantly )
If the object was being compressed by it's own weight (like a spring, the top would be compressing the lower coils) if that weight was instantly reduced the spring would expand away from the Earth as the potential energy is released from the spring.
 
On the other hand, if you simply mean an object, of mass M, sitting on the ground, reducing the mass of the object, the force of the object on the ground would be reduced but so would the force of the ground on the mass. The reduced mass would still sit on the ground, not moving.
 
However, regardless of whether or not the object is rigid or is elastic, there is no known mechanism which could cause a spontaneous loss of mass.
(Except perhaps a really tiny loss of mass over a long time if the object is radioactive and losing mass as some form of radiation.)
 
Let me rephrase the question in form of a problem.

A cube of mass 2t was sitting on some surface on Earth (so there is a force pulling it towards the center of the earth)Using the 2nd law of Newton the Earth would be pulling the objet with a force of 20kN.

And using the 3rd law of Newton the support would push the object with the same force.

If the mass of this cubic object changed to 1 kg instantly keeping the same volum.

Wouldn't the surface act as a spring at a molecular lvl and push the opject up and giving it velocity?

I understand that a suddent loss of mass can't happen but in theory what would happen?
 
RedLine said:
I understand that a suddent loss of mass can't happen but in theory what would happen?
What do the laws of physics predict if we violate the laws of physics?
That question does not have a meaningful answer.

If you put a two ton object on top of something with a mass of 1 kg, and rapidly lift the two ton object up, the 1 kg object below can jump up a bit, because the compressed floor and object will relax, pushing the object upwards.
 
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RedLine said:
If the mass of this cubic object changed to 1 kg instantly keeping the same volum.
As has been pointed out, the question is not consistent with the laws of classical physics as we know them, so the question as posed cannot be answered.

However, what I think you are actually interested in can be answered: if an elastic material is compressed by a given load and if that load is suddenly reduced then the elastic material will decompress.
 

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