From: fortunati.luigi@gmail.com   
      
   In my animation   
   https://www.geogebra.org/m/ggqgaeeb   
   there is an elevator that works with electromagnetic force and not with   
   gravity.   
      
   How does it differ from Einstein's elevator when it is restrained and   
   when it descends in free fall?   
      
   [[Mod. note -- *IF* the ratio   electromagnetic_force / mass   is the   
   same for the elevator and the test mass ("robot"), then this is indeed   
   exactly analogous to an Einstein elevator.  If this ratio differs, then   
   the weight force won't be zero when the constraint is removed (i.e.,   
   when the elevator is free-falling).   
      
   For gravity, Einstein's (weak) principle of equivalence says that the   
   corresponding ratio  gravitational_force / mass  is indeed the same for   
   *all* objects, so Einstein's elevator automatically gives zero weight   
   when its constraint is removed (i.e., when the elevator is free-falling).   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)