we know that those frame of references which are in uniform motion relative to an inertial frame of reference are called inertial frame. but the inertial frame we are using for comparing will also be in uniform motion relative to an another inertial frame of reference and that inertial will be related to another inertial frame. then how we will come to an end,mean is there any absolute inertial frame of reference which can be used for comparing?
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$\begingroup$ More on inertial frames. $\endgroup$– Qmechanic ♦Commented Jun 15, 2023 at 17:50
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$\begingroup$ That statement you've expounded just means the set of all internal frames form a group. What can be said for one can be said for all. That is a property, not a definition of inertial frames. The definition is a frame in which objects obey the law of inertia (and by extension, all 3 of Newton's Laws of Motion). $\endgroup$– RC_23Commented Jun 15, 2023 at 21:27
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4 Answers
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is there any absolute inertial frame of reference which can be used for comparing?
No, there is no absolute inertial frame. All inertial frames are equivalent and no one inertial frame is selected above another.
we know that those frame of references which are in uniform motion relative to an inertial frame of reference are called inertial frame
I think this is the source of your confusion. While it is true that one inertial frame is in uniform motion with respect to any other, that is not what defines inertial frames.
An inertial frame is a frame where any good accelerometer (6 degree of freedom type) at rest in the frame would measure no acceleration. This can be determined strictly with reference to the frame itself and does not require comparison to any other frame. Any inertial frame determined in this way is equivalent.
One caveat is that often in Newtonian physics gravity is considered a real force. Accelerometers do not detect gravitational acceleration. So in those cases you have to adjust the accelerometer reading by adding the local gravitational acceleration.
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$\begingroup$ I just want to know only that the inertial frame is at rest or moving with constant velocity to whom? is it any other frame of reference or universe ? $\endgroup$ Commented Jun 14, 2023 at 21:59
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$\begingroup$ during solving physics numericals how would i know that the frame is inertial or non inertial ? $\endgroup$ Commented Jun 14, 2023 at 22:02
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1$\begingroup$ "In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. " this is what written on WIKIPEDIA i just to want to know that to whom respect that the inertial frame is not undergoing any acceleration? $\endgroup$ Commented Jun 14, 2023 at 22:08
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1$\begingroup$ @PriyanshuChauhan I don’t like a big barrage of follow up questions. An inertial frame is at rest with respect to itself. It is moving uniformly with respect to other inertial frames. You cannot know if a frame is inertial from numericals, it is something determined experimentally as I described. The property of not accelerating is intrinsic to the frame and is not something determined with respect to any other frame, it is measured within the frame itself using accelerometers. Please do not ask another barrage of follow up questions. If you have other questions then post them as new questions $\endgroup$– DaleCommented Jun 15, 2023 at 0:38
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$\begingroup$ ok! but i did not get it. you are saying that inertial frame is at rest with respect to itself,but all frame are at rest with respect to itself. and another thing, that is you are saying that the acceleration of frame is measured with respect to acceleometers,but i am not able to get a accelerometer during my exam and to whom respect these accelerometers measured acceleration of frame $\endgroup$ Commented Jun 15, 2023 at 10:20
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is there any absolute inertial frame of reference which can be used for comparing?
No. There is no such thing as an absolute frame of reference in the universe. In other words, there is no location in the universe that is completely "stationary". Everything is moving. All motion is relative. An inertial frame of reference is simply one not undergoing any acceleration. All inertial frames are in a state of constant, rectilinear motion with respect to one another.
Hope this helps.
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$\begingroup$ I just want to know only that the inertial frame is at rest or moving with constant velocity to whom? is it any other frame of reference or universe ? $\endgroup$ Commented Jun 14, 2023 at 21:59
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$\begingroup$ during solving physics numericals how would i know that the frame is inertial or non inertial ? $\endgroup$ Commented Jun 14, 2023 at 22:02
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$\begingroup$ "In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. " this is what written on WIKIPEDIA i just to want to know that to whom respect that the inertial frame is not undergoing any acceleration? $\endgroup$ Commented Jun 14, 2023 at 22:08
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2$\begingroup$ @PriyanshuChauhan Dale gave you the answer: the physics in an inertial frame is different from the physics in a non-inertial frame. If I let go of an object in space, that object will keep floating next to me forever. If I let go of an object on Earth, then it will fall to the floor. That's how I know that my reference frame on Earth is not an inertial frame. That is what Dale meant by "accelerometer". Physics is not about solving numerical problems. It's about making observations. Nature tells you what is and is not inertial motion. $\endgroup$ Commented Jun 15, 2023 at 3:15
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$\begingroup$ ok! but i did not get it. you are saying that inertial frame is at rest with respect to itself,but all frame are at rest with respect to itself. and another thing, that is you are saying that the acceleration of frame is measured with respect to acceleometers,but i am not able to get a accelerometer during my exam and to whom respect these accelerometers measured acceleration of frame $\endgroup$ Commented Jun 15, 2023 at 10:26
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@Dale's answer is excellent, but just to expand on it a bit: proper acceleration, the acceleration experienced by an observer, is absolute and may be measured by an accelerometer or in a crude way by releasing a neutral test object and observing its motion: if it remains at rest then the frame is inertial. There's no need to compare a frame to any other frame in order to determine whether it is inertial. Of course if a frame is inertial it is in constant motion relative to all other inertial frames, but there's no universal rest frame: as far as the laws of physics go all inertial frames are equal and any one of them may be considered to be at rest.
answered Jun 15, 2023 at 1:40
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$\begingroup$ Dale is just kept telling about use of accelerometers,but during the defining of inertial frame by physicist they just do not use accelerometers,I want to know about the philosphy behind it means what is the concept behind it."for what purpose we are using an accelerometer?".and during my numerical solving in exam i will not get any accelerometer and will not perform any experiment.just want to know teachers are getting that this frame will be inertial or non inertial. $\endgroup$ Commented Jun 15, 2023 at 20:25
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An inertial frame is already a bit of an approximation, because we need to establish that it is not in accelerated motion w/respect to the universe. However, for most needs in solving problems, locally, we can think of a frame of being inertial. It is all done for the need of the (local) problem we are trying to solve, and this is sufficient.
Practically speaking, we compare the frame "with respect to something bigger", say, its non-moving environment, such as the local hills etc. But if we really need to know the full philosophy behind it, it could be looked as "stationary w/respect to the fixed stars" (e.g. Kepler) or "stationary w/respect to to the cosmic microwave background radiation", see more on Wikipedia.
For more info, see Wikipedia on inertial frames of reference
Also, very good relevant discussion about the "fixed stars" can be found here: Fixed stars
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$\begingroup$ it means the inertial frame we use for comparing with other frame is not in accelerated motion with respect to universe $\endgroup$ Commented Jun 14, 2023 at 19:57
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$\begingroup$ and can be assume any frame to be inertial as you told? $\endgroup$ Commented Jun 14, 2023 at 19:58
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$\begingroup$ Say, we are at a train station. Trains are moving on the rails... But the station itself, is an inertial frame because it is stationary. This works locally and would suffice if we look at it locally. $\endgroup$ Commented Jun 14, 2023 at 20:02
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1$\begingroup$ Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. $\endgroup$– Community BotCommented Jun 14, 2023 at 21:13
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1$\begingroup$ Please read the info above, it contains the answer to your question $\endgroup$ Commented Jun 14, 2023 at 23:16