Magnetic Rotation: Will South Pole Move to North?

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Discussion Overview

The discussion revolves around the behavior of a magnetic setup in a frictionless environment, specifically whether the south pole of a magnet will rotate towards the north pole, causing the entire system to rotate. The scope includes theoretical considerations of magnetic interactions and rotational dynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the south pole will rotate up to the north pole, leading to a rotation of the system as a whole.
  • Others question why the rotation would not occur in the opposite direction.
  • One participant expresses a desire to control the direction of rotation, referencing the behavior of a compass.
  • Another participant inquires about the relative freedom of rotation between the vertical and horizontal bars in the setup, comparing it to a compass needle's movement.
  • Participants clarify that the setup consists of four bars forming a complete cross, all of equal mass, and are examining the potential for rotation about the center due to magnetic attraction.
  • One participant asserts that an internal force cannot cause a net torque, suggesting that the proposed rotation is not feasible.
  • A later reply indicates that the discussion touches on concepts related to perpetual motion machines, leading to a closure of the thread.

Areas of Agreement / Disagreement

Participants express differing views on whether the south pole will rotate towards the north pole and whether such a rotation can cause the entire system to rotate. The discussion remains unresolved, with some participants questioning the feasibility of the proposed motion.

Contextual Notes

The discussion includes assumptions about the nature of magnetic attraction and the mechanics of rotation in a frictionless environment. There are unresolved questions regarding the interaction of forces and torques within the system.

pbhuter
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If I have a magnetic setup in frictionless, etc. area as follows:

N
/
/
/
---------------------S

Will the "south" pole rotate up to the "north" pole, causing the system as a whole to rotate?
 
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pbhuter said:
If I have a magnetic setup in frictionless, etc. area as follows:

N
/
/
/
---------------------S

Will the "south" pole rotate up to the "north" pole, causing the system as a whole to rotate?
Why not the other way around?
 
A.T. said:
Why not the other way around?
It is my understanding (and it has been awhile since magnetics in college) that it would rotate toward "north" - like a compass. But for sure I would like to be able to control the direction of rotation...
 
pbhuter said:
like a compass
Are the vertical and horizontal bars free to rotate relative to each other, like the compass needle can rotate relative the Earth? If, yes do they have the same mass ratio as the a compass needle and the Earth?
 
It is all connected. Ultimately, it is a full cross shape that I am trying to rotate about the center.
 
This is operating in a frictionless environment. Each bar is the same mass, and like I said there are four making a complete cross. I am trying to see if the whole thing will start rotating about the center as the "south pole" is attracted to the "north pole".
 
pbhuter said:
This is operating in a frictionless environment. Each bar is the same mass, and like I said there are four making a complete cross. I am trying to see if the whole thing will start rotating about the center as the "south pole" is attracted to the "north pole".

So you've effectively taken two bar magnets and put on on top of the other, offsetting one by 90 degrees?
 
pbhuter said:
causing the system as a whole to rotate?
No. An internal force cannot cause a net torque.

We don't discuss perpetual motion machines here. Thread closed.
 

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