Newtons Third Law: Cause/Effect or Simultaneous?

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Discussion Overview

The discussion revolves around the interpretation of Newton's Third Law of Motion, particularly in the context of collisions between two objects. Participants explore the nature of forces during collisions, the transfer of motion, and the implications of internal forces and energy transfer.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question whether the force exerted by object B during a collision is due to a pre-existing internal force or a transfer of motion from object A.
  • Others assert that Newton's Third Law states that forces act in pairs, with equal magnitude and opposite direction, but do not clarify the implications of this in the context of collisions.
  • A participant introduces assumptions about whether an object accelerates due to an imparted physical entity or due to its own energy responding to the collision.
  • One participant discusses the complexity of force propagation, noting that sudden impacts do not behave linearly and introduce concepts of non-linear force propagation.
  • Another participant describes the process of momentum transfer during a collision, suggesting that the ball's compression and subsequent expansion are due to intermolecular forces distributing momentum throughout the ball.
  • Questions are raised about the nature of velocity and whether an increase in velocity during a collision can be viewed as a positive addition to the object's mass, leading to a discussion about the positivity of velocity as a physical entity.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of forces during collisions, with no consensus reached on the interpretation of Newton's Third Law or the mechanisms of energy transfer. Multiple competing perspectives remain throughout the discussion.

Contextual Notes

Participants acknowledge the assumption of perfectly rigid objects in experiments, which may not hold true in real-world collisions. The discussion also highlights the complexity of force interactions during sudden impacts, suggesting that traditional linear models may not apply.

omin
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When object A and object B collide, where A is moving and B is stationary and where B seems to compress:

Does B expand in response because a pre-existing internal force exists in B and exerts an equal and opposite reaction, or

Is the entity motion transferred from A to B redirected back at A from B the equal and opposite force in return?

If A and B were the exact mass and had a collinear collision and both went in equal and opposite directions, is this proof of internal forces that change the direction or a transfer of the entity motion?

If A causes B to accelerate after the collision, is:
1. the force of B exactly the same as before
2. the force of B the same as before, but more force because of the new velocity, or
3. the same force as before, but the new velocity is a new shape of the same medium in which the same value of force is expressed?

I'll take any response.
 
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I have no idea what you are saying, but I'll state the third law in simple terms.

Whenever a force is acted on B by A, a force equal in magnitude and opposite in direction is acted on A by B simultaneously.

Consequences:
1. Forces must work in pairs. It's impossible for any force to exist on it's own.
2. The action-reaction pairs must act on different objects, in different directions.

Did it help?
 
Let me try again.

Assumption #1 I assume when an object accelerates, the object that it contacts is imparted with some 'physical entity' to it to make it move faster.

Assumption #2 I also assume 'no physical entity' is imparted, and that no object has has anything extra because it's moving faster or has anything less because it's moving slower.

After a baseball is hit, the baseball flys away from the bat because of energy given to it by the bat or the base ball accelerates because it's own equal and opposite energy is repsonding to itself?
 
omin said:
When object A and object B collide, where A is moving and B is stationary and where B seems to compress:

Does B expand in response because a pre-existing internal force exists in B and exerts an equal and opposite reaction, or

Is the entity motion transferred from A to B redirected back at A from B the equal and opposite force in return?

If A and B were the exact mass and had a collinear collision and both went in equal and opposite directions, is this proof of internal forces that change the direction or a transfer of the entity motion?

If A causes B to accelerate after the collision, is:
1. the force of B exactly the same as before
2. the force of B the same as before, but more force because of the new velocity, or
3. the same force as before, but the new velocity is a new shape of the same medium in which the same value of force is expressed?

I'll take any response.


What you are asking may seem simple but it is, in reality, extremely complicated.
The following is not an answer to your question but a general comment of the subject matter.

You question(s) bring to mind the concept of non-linear force propagation, meaning that a shock wave does not behave the same as a linear "push"
A gentle "push" of one object to another obey's classical linear laws of force transfer. However, a sudden impact does not.
The force propagation of a sudden impact is not linear, it is spherically expressed, and it's effects are not well understood.
 
First, we must remember that in most of the experiments that we do, we assume the objects to be perfectly rigid, which is not the case in this one. The ball is compressed when being hit.
Okay, back on topic. This is only a gues though, so feel free to correct it if you find anything wrong. The bat hits the ball. A lot of momentum is transferred to the ball. However, since only part of the ball is in contact of the bat, the other part has not yet felt a force to move forward(away from the bat). So, the part that touches the bat collides into the part that doesn't touch, and this causes the ball to be compressed. The momentum is then quickly distributed over the ball by the intermolecular forces within the ball, and soon every part of the ball is moving forward with the same velocity. The ball is hence expanded back into it's original shape and zooms away.
So it's a transfer of energy from the bat, to "some of the ball's particles", and then "all of the ball's particles". The ball itself cannot "create energy", but it helps transfer momentum to "un-moving" particles to help create motion. Otherwise, the ball would tear apart.
 
kuenmao said:
The momentum is then quickly distributed over the ball by the intermolecular forces within the ball...
...it's a transfer of energy from the bat, to "some of the ball's particles", and then "all of the ball's particles". The ball itself cannot "create energy"...

If I accelerate something and the mass of that thing is constant before and after the collision creating the acceleration, is an increase in velocity equivalent to a positive thing I am adding to the accelerated object's mass?

Displacement of mass is obvious to everyone. Everyone has seen things move. But if the mass is constant before and after a collision and the velocity increase is proportionately to a decrease betweeen two colliding objects, isn't this displacement of velocity? Isn't velocity being displaced? All things of the physical world I sense are positive. Isn't then velocity a positive entity? What positive thing does velocity represent?
 
I'm not sure what you're talking about. Perhaps you should as someone else...
 

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