From: fortunati.luigi@gmail.com   
      
   Luigi Fortunati il 24/03/2024 07:29:00 ha scritto:   
   > [[Mod. note -- Perhaps.   
   >   
   > That is, let's call your 1-gram body "A", and your 2-gram body "B".   
   > We can think of B as a pair of one-gram halves (call them "B1" and "B2")   
   > glued together.  The question is, does the presence of B1 change the   
   > electromagnetic (EM) field at B2's location, or vice versa, by an   
   > amount large enough that we need to care about it?  If *not*,   
   > then the EM force acting on B will be the sum of   
   > (a) the EM force acting on B1 alone (i.e., if B2 were NOT there), and   
   > (b) the EM force acting on B2 alone (i.e., if B1 were NOT there).   
   > Assuming that B is small enough that the EM field doesn't vary   
   > significantly across B's diameter, we should have (a) = (b), so in   
   > this case the EM force acting on B should be twice the EM force   
   > acting on A.   
   >   
   > But, if the presence of B1 *does* change the EM field at B2's location   
   > by a significant amount, then the EM force acting on B will *not*   
   > equal the sum of (a) and (b) above, and the EM force acting on B will   
   > *not* be twice the EM force acting on A.   
      
   This thing you say also applies to the gravitational field: if the presence of   
   B1 changes the gravitational field at the position of B2 by a significant   
   amount, then the gravitational force acting on B is not equal to the sum of   
   (a) and (b ) and the    
   gravitational force acting on B is not double the gravitational force acting   
   on A.   
      
   The proportionality between force (whether gravitational or EM) and mass   
   depends on each individual particle because it is precisely the particle that   
   intercepts its share of the field force (whether gravitational or EM).   
      
   Obviously (and to avoid any misunderstanding) the comparison must be made   
   between equal materials and, that is, if the material of the first body is   
   XYZ, that of the second body is also XYZ (if the material of the first is   
   iron, that of the second is    
   also iron , if one is wood the other is also wood).   
      
   Luigi Fortunati   
      
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