Supposing I am in a non-inertial system and I don't know what forces are acting. How can I test EXPERIMENTALLY and in practice to be in a non inertial system? If I am in a system and I don't know how does it moves and I would make an experiment to test if this is inertial or not, what should I do? For example: in a lift? In a rotating system?


1 Answer 1


Inertial frame of reference is such that free bodies move with constant velocity. If you detect free body accelerating, the frame is not inertial.

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    $\begingroup$ How can i say that a body is free ? With an experiment if the system where i am is not inertial. $\endgroup$
    – user85480
    Jul 9, 2015 at 23:22
  • $\begingroup$ This is all well and good, but it is not really complete without a discussion of gravity in classical physics versus in general relativity. Or a link would do. $\endgroup$ Jul 9, 2015 at 23:25
  • $\begingroup$ @IlarioVitali, body is free if no other body interacts with it. In practice, approximately free body is body for which the effect of the interaction is negligible during the time period of interest. $\endgroup$ Jul 10, 2015 at 18:22