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Why does every action have an equal and opposite reaction?
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This was a completly inapproiate response to a students question. I will not tolerate such garbage here.Originally posted by anand
Why does every action have an equal and opposite reaction?
Thats a tough question because it is something that seems (to me at least) to be self evident: It just does. So let me turn it around - is there something that leads you to believe it wouldn't?Originally posted by anand
Why does every action have an equal and opposite reaction?
There exists a casual geometrical explanation of action, reaction and theit subsequent resultant(s).Originally posted by anand
Heh heh.Actually I am a high school student.So, I don't really understand what you mean.Could you please explain?Any way,thanks for replying.
Specifically, every force has an equal and opposite force. This is because of conservation of momentum. Force is a change in momentum over time. If momentum is conserved, then it cannot change with time. That means that if you apply a force to change the momentum of part of a system, there must be an opposing change in momentum (force) to keep the total change in momentum equal to zero.Originally posted by anand
Why does every action have an equal and opposite reaction?
Where you repeat experiments in the 'exact' manner, results show no deviaition from observed effects, you do something and something happens as a result, technically you cannot repeat any 'event' in exactly the same 100% way, Entropy will force you to comply to its natural path!Originally posted by anand
Why does every action have an equal and opposite reaction?
This is has been the best formal anwer yet.Originally posted by Ambitwistor
Specifically, every force has an equal and opposite force. This is because of conservation of momentum. Force is a change in momentum over time. If momentum is conserved, then it cannot change with time. That means that if you apply a force to change the momentum of part of a system, there must be an opposing change in momentum (force) to keep the total change in momentum equal to zero.
So, your question has been reduced to the question, "Why is momentum conserved?" If you study the Lagrangian formulation of mechanics, you learn that conservation laws are due to symmetries. (This is known as "Noether's theorem".) In this case, the law of conservation of momentum is due to a spatial translation symmetry. In plain terms, the outcome of an experiment should not depend on where it is performed. So if you move from one place to another ("translation in space"), the laws of physics are unchanged ("the laws of physics are invariant under spatial translation"). Noether's theorem says that there must then be a conserved quantity, which we call "momentum".
So, your question has been further reduced to the question, "Why are the laws of physics the same at all locations?" We don't know. Maybe they aren't ... they are as far as we know, but we can't know for sure.
Conservation of energy is due to invariance under time translations.Originally posted by Rybo
"Conservation of momentum" sounds much like "conservation of energy."
There isn't any symmetry that gives rise to "conservation of inertia". But in relativity, conservation of energy becomes conservation of mass-energy, and mass-energy is representative of inertia in some senses.
I would informally extrapolate from those statements a "conservation of inerta" as well.
It's due to the laws of physics in the universe having certain symmetries.
Why these three and others are conserved is due to the physical Universe being a finite integral whole.
Well, you can appeal to the weak anthropic principle, but there isn't any theoretical reason why a universe without these symmetries couldn't exist.
Why are the laws of Universe the same everywhere in Universe as far as we know?
Beacuse if they werent the integrity of our physically finite whole of Universe would not exist.
That isn't true for static forces as there is no momentum or energy change.Originally posted by Ambitwistor
Specifically, every force has an equal and opposite force. This is because of conservation of momentum. Force is a change in momentum over time.
It is true for static forces. That there is no momentum or energy change is my whole point: that is why for every force, there is an equal but opposite force. If A exerts a static force on B, then B exerts an equal but opposite static force on A, to ensure no net momentum or energy change.Originally posted by russ_watters
That isn't true for static forces as there is no momentum or energy change.