1. Can we experimentally check that the 1st Newton law is true in our nature?
2. Could we determine mass m or force F independently in the 2nd Newton law F=ma? What is the 2nd law? It seems to me is not even a determination of a force...(because m is unknown)
3. How is about a velocity, acceleration and kinematics at all? How do we determine physically even the straight line and the coordinate system in kinematics? Through the optics, light raws? But is the light raw satisfied ALL EUCLEAD GEOMETRY AXIOMS?..;) It is not ! We can not divide the light raw by infinite number of parts so continuity, Archimedes axioms are not valid for light or any metal rods, threads, etc. You maybe know that parallelity (the 5th euclead axiom) axiom for any real life object can not also be checked in principle!
4. What is about the 3rd Newton law. It is frequently presented as momentum conservation law. But this 3rd law is valid in the absence all other forces, e.g. in the closed system. So the 3rd law can not be also checked if we do not determine a force F from the 2nd law.
5. All we can do using physics is to check the CONSEQUENCIES which are deduced from ALL PHYSICS and GEOMETRY LAWS together (WHICH WE TOOK FOR GRANTED).For example we can determine inertial mass m using a balance (the theory of which requests all three Newtons laws and also angular momentum law and the faith of that geometry laws could be applied)
6. Is it possible to construct the physics laws that are (not only their consequencies) all experimentally checked?
These are my humble oppinions on some of your very interesting questions. I am sure many of my peers will disagree :-)
Newton's postulates for particle motion (Newton's laws) are not testable individually. It is not required for a postulate to be testable, it is only required for the implications of the theoretical frame as a whole to be testable (a view that you already express in item 5).
My own, current view on the role of Newton's three laws is as follows:
1st law) The first law is stated without reference to the character of force, so that the word force can be viewed as a representation for general interaction. I read it "No interactions => Constant velocity", which is fundamentally different from "Sum F = 0 => a = 0", since the latter utilizes the vector quality of the force. This introduces the idea of an inertial frame of reference. It is a postulate that cannot be tested, since we cannot isolate a body from the rest of the universe. Within the theoretical frame, the only place where truely isolated particles can exist, this gives a precise meaning to the concept of acceleration without knowing the exact nature of interactions.
2nd and 3rd law) The second and third laws together depict the nature of interactions, including their additive nature. The force vector is usually introduced as a mathematical tool to describe this additivity. There is no way to quantify (measure) forces without introducing additional particular laws, force laws. Mass, on the other hand, is properly defined by 2nd and 3rd (Griffiths 1985, "Theory of classical dynamics"), which is frequently described in text books: For a particle pair, A and B, interaction, these laws give m_A a_A = m_B a_B, which can be used to establish the concept of mass. (It is a strange and beautiful thing that this mass also enter the law of gravity)
Dear Stefan B Lindström,
I am very glad that you replied to my question which maybe is not very nice (rather boring) for physicists :)! But anyway everybody should come to it now or after...:)
At the end of your message you presented classical textbook way to determine an inertial mass m from the 3rd law, in other words from momentum conservation law. But your determination of mass m requests the notion of force F (!!!) as in your case there should not be any other forces besides of two forces of particles A and B. So you CAN NOT determine an inertial mass m by such a way.
Best wishes,
Anatoly
Dear Sirs,
You read these and above strings. Would it seems to you that the physics is indeed a TRULLY MYSTERIOUS (say forthrightly MAD!!!) DEVICE which allows us to make true (I do not know WHY!??) consequences about nature? Who from physicists is sure that the next consequence from the physics laws will work in nature? I think - nobody!
Somebody else, maybe a God :) (I joke), gave to Newton this "fairy wand" and this device works well in our mad world. Companies make money, others make bombs, another makes our homes and cures our relatives and the later is a great thing ...
But I can not get rid of the thought that the physics is in somewhat a mad thing..
Can anybody turn me to optimistic positive way?
Dear collegues-physicists!
I understood after about 2 week silence on my question the following. You can add nothing to my question.. :) It is funny isn`t it :). Thanks for my fun mood :))
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