From: fortunati.luigi@gmail.com   
      
   Gravity manifests itself as gravitational force if there is an obstacle   
   (the stone on the wall of the well) and as gravitational acceleration if   
   the obstacle is not there (the same stone as before that detaches from   
   the wall and falls).   
      
   In the first case there is gravitational force (and there is no   
   acceleration), in the second case there is gravitational acceleration   
   (and there is no force).   
      
   When in my animation https://www.geogebra.org/m/eybpyx4d we click on the   
   "Detach the stone from the wall" button, the stones A and B detach from   
   the walls and fall.   
      
   In this phase of free fall, the two stones A and B accelerate towards   
   each other and, therefore, they are two mutually accelerated reference   
   systems: how can they both be declared inertial if they are accelerating   
   towards each other? Can inertia and acceleration coexist?   
      
   Note that I am talking about (gravitational) acceleration and not force.   
      
   Luigi Fortunati   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)