Law of conservation of 'force'.

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    Conservation Force Law
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Discussion Overview

The discussion centers around the concept of force, particularly the idea of a "law of conservation of forces" and its relationship to established principles such as Newton's laws and the conservation of momentum. Participants explore whether the net force acting on an object can differ from the applied force and the implications of this for isolated and non-isolated systems.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants propose that if a force is applied in one direction, the net force on the object cannot differ from the applied force in that direction.
  • Others argue that this concept relates to the law of action and reaction, suggesting that forces come in equal and opposite pairs.
  • One participant mentions that force can be considered conserved in an isolated system, but questions whether this represents a new conservation law.
  • Another participant distinguishes between constant forces and conserved forces, stating that conservation typically applies to properties rather than external forces.
  • Some participants discuss the implications of a hypothetical "law of conservation of forces," suggesting it could derive from the conservation of momentum.
  • A participant raises concerns about the definitions and assumptions underlying the discussion, indicating confusion about the variables used.
  • There is mention of a conservative system, such as a lever, where forces can differ unless certain conditions are met.
  • One participant expresses uncertainty about the existence of a "law of conservation of forces" and its relation to established conservation laws.

Areas of Agreement / Disagreement

Participants express differing views on the existence and implications of a "law of conservation of forces." While some agree on the relationship between force and momentum, others challenge the applicability of conservation laws to non-isolated systems. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight limitations in their understanding of conservation laws, particularly in relation to isolated versus non-isolated systems. There is also ambiguity regarding the definitions and implications of terms like "constant force" and "conserved force."

dE_logics
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If force is applied in one direction, then it can't happen that the net force application on the normal reactant (or the stuff on which the force finally falls on) is more than or less than the applied force in the same direction as the applied force.

Is this correct?

What I mean to say here is that suppose a force (x) applies through a mechanism and all the force finally falls on something...or there's just 1 object on which the force falls on (take the magnitude of the force that falls on this object as y)...so can it happen that x != y?
 
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dE_logics said:
Is this correct?

What I mean to say here is that suppose a force (x) applies through a mechanism and all the force finally falls on something...or there's just 1 object on which the force falls on (take the magnitude of the force that falls on this object as y)...so can it happen that x != y?

Aren't you stating the law of action and reaction?
 
russ_watters said:
Correct: forces come in equal and opposite pairs.
The Newton equations read:

M1a1 = -∂U(X1-X2)/∂X1 = F12

M2a2 = -∂U(X1-X2)/∂X2 = -F12

Note that F12 and -F12 enter different equations (whatever masses are). So there should be a relative motion due to interaction.

The forces come together in the center of inertia R equation:

Mtot∂R/∂t = F12 - F12 = 0

That is why they say that internal interactions do not influence the CI motion.
 
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Force is the change in momentum wrt time, so since the momentum of an isolated system is conserved the change in momentum wrt time is zero which is constant wrt time and therefore also conserved. So you could indeed say that force is conserved for an isolated system.

However, since the definition of an isolated system is a system with no external force then all you are saying is that if the external force on a system is always zero then the external force on the system is constant. I don't think this represents a new Noether charge or current.
 
If there is a force independent of time and space it is called a constant force, not a conserved.

The force is something external acting on a particle (see Newton equations). There may be laws of conservation of particle "properties" or ensemble of particle "properties", not of the external things.
 
Bob_for_short said:
If there is a force independent of time and space it is called a constant force, not a conserved.
The statement "X is conserved" means dX/dt = 0. So if F = 0 (isolated system) then dF/dt = 0 and it is reasonable to say "force is conserved", although I agree with you that it sounds weird and the usual statement would be that it is constant.
 
Hello de logics-
I can design a conservative system such as a lever, where F1x1 = F2x2, but F1 <> F2 unless x1 = x2 . Is this what you mean?
Bob S
 
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Where did my post go??...I posed here 'thanks'.

Actually I think I missed a few posts.
 
  • #10
tanujkush said:
Aren't you stating the law of action and reaction?

This if such a component existed, the law of conservation of momentum would have been trash.

@DaleSpam

No, that was not the question actually; an isolated system is out of the question here.



It appears we have a sort of chaos here && I don't know the meaning of the various variables used.

What I think, this is a necessity cause if the force applied through this mechanism and to a body is more or less than the actual force applied, the momentum delivered to the body will be more or less than the momentum possessed by the colliding body.

So there should be some "law of conservation of forces"...it's derived from the law of conservation of momentum.

Even during lever action, this law holds true.

Search "law of conservation of forces"...we have only 7 results (yes, I know Google search is VERY inaccurate...like Google desktop and so this post is not shown...maybe it need time to reindex.).
 
  • #11
Ok then...final question; does this law exit?
 
  • #12
dE_logics said:
So there should be some "law of conservation of forces"...it's derived from the law of conservation of momentum.
The "force law" leading to conservation of momentum is Newton's 3rd law. Is that all you mean?
 
  • #13
Yes, sort of everything is indirectly related...I think.

Since impulse is a function of force and under any collision, the impulse delivered to another body (B) is equal to the momentum possessed by the colliding body...this is the law; so, by this law there can't be a mechanism which reduces or increases this force without any change in time or area.

I did a few calculations...and according to them, if such a mechanism does exits, it will be against the law of conservation of energy.
 
  • #14
dE_logics said:
No, that was not the question actually; an isolated system is out of the question here.
...
So there should be some "law of conservation of forces"...it's derived from the law of conservation of momentum.
I don't think you understand the standard conservation laws. They all apply only to isolated systems. Momentum and energy are not conserved for non-isolated systems.
 
  • #15
aaaa...I was wondering there was an application of force from the outside here...if it's inside the system, then it's isolated (and I was not assuming that).

Anyway, I get what you mean, I'm on the same foot as all of you.
 
  • #16
So finally am I right?
 
  • #17
What is your current understanding?
 
  • #18
This -

If force is applied in one direction, then it can't happen that the net force application on the normal reactant (or the stuff on which the force finally falls on) is more than or less than the applied force in the same direction as the applied force.
 
  • #19
I think that is correct, although rather confusingly worded.
 
  • #20
:D...ok then thanks.
 

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