From: fortunati.luigi@gmail.com   
      
   Il 19/02/2026 02:43, Luigi Fortunati ha scritto:   
   > Il 18/02/2026 04:23, Luigi Fortunati ha scritto:   
   >> In an internal combustion engine, energy is generated and then channeled   
   >> in one direction, and that scalar energy becomes a vector force.   
   >>   
   >> Therefore, we can consider energy as a set of equal and opposite forces   
   >> directed in all possible directions.   
   >>   
   >> Thus, energy, despite being composed of vector forces, is a scalar   
   >> simply because none of these forces prevails over the opposing force.   
   >>   
   >> However, if at a certain point one of these forces increases or   
   >> decreases without the opposing force doing the same, part of this energy   
   >> becomes a vector force.   
   >>   
   >> Is this correct?   
   >>   
   >> Luigi Fortunati   
   >>   
   >> [[Mod. note --   
   >> No, in general it's not correct.  Energy and force are two different   
   >> things, and it's not correct is to say that energy is composed of   
   >> forces.   
   >>   
   >> Energy is the ability to do work, and an important special case of   
   >> this is mechanical work, where a force acts on a body which moves.   
   >>   
   >> But, there are (other) types of energy which aren't associated with   
   >> mechanical work.  For example, think about the energy carried by   
   >> electromagnetic radiation (e.g., sunlight), or more generally, by the   
   >> energy contained in a (large) set of photons.   
   >> -- jt]]   
   >   
   > Okay, in general, that's not correct, but in one particular case, it is.   
   >   
   > In a balloon, the internal air particles continually collide with the   
   > walls, keeping it inflated.   
   >   
   > In this case, we can say that the sum of all the forces exerted by the   
   > air particles against the walls of the balloon is internal "energy,"   
   > without direction.   
   >   
   > [[Mod. note --   
   > No, we can't (correctly) say that.   
   >   
   > One way to see this is to compare two balloons A and B, both having   
   > the same shape, and both inflated to the same pressure, but with B   
   > being 10 times the diameter of A.   
   >   
   > B has 1000 times as much volume of A, so compressing the air into B   
   > required 1000 times as much energy as compressing the air into A, and   
   > puncturing B can release 1000 times as much energy as puncturing A.   
   >   
   > Since both balloons are inflated to the same pressure, the force   
   > exerted by the compressed air on each square cm of B's outer skin   
   > is the same as the force exerted by the conpressed air on each   
   > square cm of A's outer skin.  B has 100 times as much surface area   
   > as A, so the sum (really a surface integral) of all the forces   
   > exerted by the compressed air against B's outer skin is 100 times   
   > as much as the sum (surface integral) of all the forces exerted by   
   > the compressed air against A's skin.   
   >   
   > Comparing A vs B, we see that B stores 1000 times as much energy,   
   > but has only 100 times as much total-force-on-outer-skin.  Since   
   > energy varies *differently* from the total-force-on-outer-skin,   
   > these things can't be the same.   
   > -- jt]]   
      
   Everything is correct as always, but I wrote other things.   
      
   Referring to the energy of the inflated balloon (and not to other   
   energies), I wrote that...   
      
   1) The scalar energy of the inflated balloon is the set of vector forces   
   of the air pushing against the walls.   
      
   2) This energy, despite being composed of vectors, is scalar because,   
   for every force pushing to the right, there is another pushing equally   
   to the left, and for every force pushing up, there is another pushing   
   down, and so on.   
      
   3) The presence of these equal and opposite forces ensures the mutual   
   cancellation of all the forces present, so no vector quantity remains.   
      
   All this persists as long as the balloon remains inflated, but ceases to   
   exist when it punctures (for example) on the right.   
      
   In this case, the internal forces pushing to the left (and no longer   
   balanced by those pushing to the right) take over and accelerate the   
   balloon to the left.   
      
   The same forces that formed the internal scalar energy of the inflated   
   balloon now become the net force *vector*, which accelerates the balloon   
   according to the second law, F=ma.   
      
   That said, why am I interested in the connection between energy and force?   
      
   I'm interested because the stresses that occur at the point of contact   
   during the collision create two distinct and separate energies, one for   
   each body, with two different histories.   
      
   Luigi Fortunati   
      
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