A paradox inside Newtonian world

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    Newtonian Paradox
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Discussion Overview

The discussion revolves around a proposed paradox within Newtonian mechanics, specifically related to gravitational forces and the motion of masses in a system. Participants explore the implications of mass distribution, gravitational influence, and the behavior of the center of mass in this context.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Thomas presents a paradox involving gravitational forces and questions whether his reasoning is flawed.
  • Some participants assert that Thomas's calculations contain errors, suggesting that a thorough review is necessary to identify these mistakes.
  • One participant argues that the gravitational influence of closer, smaller masses outweighs that of more distant, larger masses, leading to a net force directed to the left.
  • Another participant emphasizes the importance of considering the net force on each mass, referencing Newton's Third Law and suggesting that the center of mass should not accelerate.
  • There is a contention regarding the behavior of the center of mass, with some suggesting it may not move left as initially proposed, while others maintain that the gravitational pull from the left will dominate.
  • Participants discuss the implications of infinite mass distributions and the potential for paradoxes arising from such scenarios, with some suggesting that the situation may be unphysical.
  • There is a proposal to analyze the system with a finite number of masses and then consider the limit as the number of masses approaches infinity.
  • Concerns are raised about the treatment of forces and the singularity at the origin, with suggestions that this may contribute to the paradox.

Areas of Agreement / Disagreement

Participants do not reach a consensus, with multiple competing views on the validity of the paradox and the implications of gravitational forces in the described system. Disagreements persist regarding the calculations and interpretations of forces acting on the masses.

Contextual Notes

Limitations include the dependence on the assumptions about mass distribution and the treatment of infinite systems, which may not align with physical reality. The discussion remains open to interpretation and further analysis.

  • #511
Yes because the force on the center of mass will be equal to the sum of the forces on all particles in the system. Thus the forces add to be infinite. This is a problem.
 
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  • #512
First of all, the force to the mass center is NOT the sum of all forces. Not at all.

Do you know that?
 
  • #513
Tomaz Kristan said:
First of all, the force to the mass center is NOT the sum of all forces. Not at all.

Do you know that?
It hadn't occurred to us.

M\mathbf{R} = \sum_i m_i \mathbf{r}_i
M\dot{\mathbf{R}} = \sum_i m_i \dot{\mathbf{r}_i}
M\ddot{\mathbf{R}} = \sum_i m_i \ddot{\mathbf{r}_i}
 
  • #514
Do you know, that this is not the case?

You and I could be forced to accelerate in the opposite directions, yet the center of the mass of the you&me system, would not move at all. Let alone to be accelerated.

Just one example.
 
  • #515
This thread has gone long enough, and I believe that nothing has been achieved. This topic is now closed, and no new ones should be opened related to it.

Zz.
 

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