Arm-wrestling -- question about forces

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Discussion Overview

The discussion revolves around the forces involved in arm-wrestling, particularly focusing on the relationship between the forces exerted by two competing hands and the implications of Newton's third law. Participants explore the dynamics of force and torque in this context.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that when hand A prevails over hand B, the force of A on B cannot exceed the force of B on A, citing Newton's third law.
  • Others argue that the torque exerted by hand A on hand B is greater than the torque that hand B can generate, suggesting a distinction between force and torque in this scenario.
  • A participant mentions the need to differentiate between muscular force and the total force exerted, indicating that hand B's force could remain constant even if B stops pushing.
  • Another participant highlights that while hand A may exert a consistent force initially, practical limitations such as power constraints and the table's interference will eventually affect the dynamics.

Areas of Agreement / Disagreement

Participants do not reach a consensus, with multiple competing views on the relationship between the forces exerted by the hands and the implications of Newton's laws. The discussion remains unresolved regarding the precise dynamics at play.

Contextual Notes

There are limitations in the discussion regarding the definitions of "strength" versus "force," as well as the assumptions about the conditions under which the forces are applied. The role of torque and the effects of practical constraints are also noted but not fully resolved.

Luigi Fortunati
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In the arm-wrestling, when the hand A prevails on the hand B, the force of A on B is greater than that of B on A?
 
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Luigi Fortunati said:
In the arm-wrestling, when the hand A prevails on the hand B, the force of A on B is greater than that of B on A?
No. That would violate Newton's third law. The torque on the arm of B from the force from A is greater than the torque on the arm of B that B is able to generate.
 
Luigi Fortunati said:
In the arm-wrestling, when the hand A prevails on the hand B, the force of A on B is greater than that of B on A?
No, see also this:
http://www.lockhaven.edu/~dsimanek/physics/horsecart.htm
 
A.T. said:
No, see also this:
http://www.lockhaven.edu/~dsimanek/physics/horsecart.htm
OK thanks.

Therefore the force exerted by the hand A (also of the strongest man in the world) on the hand B, can never exceed (not even a little) the strength that the hand B exerts on the hand A (therefore represents its maximum limit).
 
Luigi Fortunati said:
OK thanks.

Therefore the force exerted by the hand A (also of the strongest man in the world) on the hand B, can never exceed (not even a little) the strength that the hand B exerts on the hand A (therefore represents its maximum limit).
“Strength” is not a standard physics concept. Do not confuse it with force, which is.
 
Luigi Fortunati said:
OK thanks.

Therefore the force exerted by the hand A (also of the strongest man in the world) on the hand B, can never exceed (not even a little) the strength that the hand B exerts on the hand A (therefore represents its maximum limit).
I think you need to distinguish between the muscular force and the total force one hand exerts on the other.

For example.. the force B exerts on A could stay the same even if B gives up and stops pushing. If A keeps pushing with the same force then when B gives up hand B will start accelerating and that will make up for the loss of muscular force B was applying on A.

In practice hand A won't be able to maintain the same force on B for very long but while it can hand B will exert the same force on A. Eventually he table will get in the way or hand A will be power limited (power = force * velocity and the velocity is increasing).
 

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