The girl and the magnets

The girl long hair ribbon is left alone in an empty room with two identical steel bars , except that one is magnetized and the other not. To be finally free, it must determine which one is magnetized . The bars are heavy, solid , UNBREAKABLE and no hardware is available. 

 

How will it take them ?

 

 

 

 

 

 

Answers : 

 

 

In this problem we are capable of any immediate reference. The resolution is of type ' all or nothing ' . But it may well insconscient after an inside job. The solution exists and it is simple . We must break symmetry . But here the solution must be purely physical and manipulable objects are the only two bars , and ... the tape . The magnetic attraction is completely symmetric with respect to two bars, it does not mean that attracts and is attracted ... except precisely one point: the one corresponding to the middle of the bar magnet , which by symmetry it can be magnetized . Therefore determined the middle of one of the bar B. For this, ' take ' the length thereof with the tape. Is folded into two the part of the ribbon which corresponds to the length of the bar to determine the environment. So we present another A perpendicular to the middle of the bar B.

Si rien ne se passe, alors la barre A n'est pas aimantée, puisqu'elle n'attire pas le milieu de B. C'est donc la barre B qui est aimantée.

Si, il y a attraction , c'est la barre A qui est aimantée et attire la barre B non aimantée.