From: fortunati.luigi@gmail.com   
      
   In the animation https://www.geogebra.org/classic/uyhpg8ug, there are   
   two equal and opposite external forces (F1=+100 and F2=-100) acting on   
   particles A and B of body A, which is not accelerating.   
      
   By clicking on the appropriate buttons, you can display (or hide) forces   
   F3 and F4.   
      
   My question: does only force F1 act on particle A (and nothing else) or   
   does force F3 also act?   
      
   And does only force F2 act on particle B (and nothing else) or does   
   force F4 also act?   
      
   My question concerns only the forces acting on particles A and B of body   
   A, not those acting on other bodies not shown in the animation.   
      
   Luigi Fortunati   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)