![]() ![]() (To make sure personally you can take a lump of clay and knead it until you are sure it's all uniformly mixed.) You start with a bulk quantity of something uniform. We know we can do setups with air tracks, to get near frictionless motion. The defninitions that we are using in the course of doing physics are operational definitions. Theory, concept, law, and method of measurement - forever inseparable - are born into the world in union. Principle deprives one of the means properly to define or even useĪny forward step in human knowledge is creative in this sense: that Contrariwise, the absence of some body of theory, law, and Have this deep and subtle character, that they both define theĬoncepts they use (here B and E) and make statements about theseĬoncepts. The discussion in section 3.1 of the book goes as follows:Īll the laws and theories of physics, including the Lorentz force law, Physics, including Newton's laws of gravity, have this deep and subtleĬharacter, that they both define the concepts they use (here GalileanĬoordinates) and make statements about these concepts." 'Define your terms before you proceed.' All the laws and theories of Least by Henri Poincaré, that view is out of date which used to say Slightly modified): "Here and elsewhere in science, as emphasized not System and its nonuniqueness? Answer: (a quotation from par. Only afterwards (here) com to grip with the nature of the coordinate ![]() Properties of spacetime in Galilean coordinates first (par. Point of principle: how can one write down the laws of gravity and ![]() ![]() The following paragraphs go into the question of how to do physics at all. The issue that you raise is addressed in the book 'Gravitation', by Misner, Thorne, and Wheeler. I should mention that I did not find any other questions on the Physics Stack Exchange properly addressing my question. If you think that this question needs modification or clarification, do not hesitate to tell me. Newton's law (2) states that "acceleration is force". I am pretty convinced that the earth is not an inertial frame of reference and pretty aware that in the appropriate frame of reference in which Earth is rotating, the "fictitious force" is just incorporated in the acceleration. Just to be clear, I am not a first-year undergraduate student who does not understand anything to Newtonian physics. My objection is then: why do we say that this frame of reference is not inertial, rather than admitting that we forget a force in our inventory? To restore the equality one has to add a "fictitious" force, $F_f$, so that $ma=F F_f$. Then one observes the acceleration of the pendulum $a$, and observe that $ma\neq F$. To do so, one cooks up an inventory of forces, let us say that all these forces add up to $F$. Let me give a troubling example, may somebody explain to me why I am wrong: Foucault's experiment is considered as a proof that the frame of reference given by the earth in which we are sitting in, is not an inertial frame. Is there a rigorous construction of mass, force, and Newton's first/second law? which requires the notion of force to be defined! And the force is also by definition ma in intertial frames. With this notion of mass, you identify $F$ as the thing equal to $ma$.īut in order to do so, you need to work in inertial frame of references. It seems that the second Law (2) is a definition of both force and mass: you measure a and you observe that there is a proportionality constant $m$ depending on the object such that $m_1a_1=m_2a_2$ when the two objects are in the same conditions. These statements are somewhat "circular", this is no news as many other questions on this SE can attest this fact. (1) An inertial reference of frame is, by definition, a frame in which if there are no net forces, that is, if the sum of all forces acting on an object is equal to zero, then $a=0$. My understanding of Newtonian's law is the following (I will not talk about Newton's third law): (iii) Force is to be defined too and, of course, a way to measure it. How can we define such a notion? How can we measure it? I'll consider that it is possible to measure it so that acceleration in a given reference frame is computable. (i) Position and time in reference frames. In a "modern way of teaching Newtonian mechanics", there are several notions to define before stating Newton's laws, which appear in the laws. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |