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In energy–momentum relation =. From which rest frame is supposed to be captured?

mirt
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  • Why do you think there is a frame from which it is "supposed" to be captured? If this is about the energy being frame-dependent, see https://physics.stackexchange.com/q/154842/50583 – ACuriousMind Aug 14 '19 at 17:16
  • thanks for this link! upd: i've ask you a question there – mirt Aug 14 '19 at 17:17

2 Answers2

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Equation $p=m\gamma \nu$ holds in any inertial frame, where $\nu$ is the velocity of some object of interest in that frame.

  • Suppose we have neutrino that is traveling with near the speed of light. Suppose that neutrino flies near my body. From the rest frame of neutrino i'm traveling with near the speed of light. Should i use this speed in = to compute my body E with energy–momentum relation? – mirt Aug 14 '19 at 16:06
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The equation can be used in any inertial frame of reference. It must be inertial, those special frames in which these laws are valid.

Reading your comments to some other answers, let me remind you that things like Energy, Momentum, Work, etc. are Frame dependent. They change according to the frame used. But laws like conservation of energy, momentum, etc. are valid in any of these frames. Like in some frame you get your energy to be 20 kJ, then until something do work on you your energy will remain 20 kJ. In some other frame of reference, if you get your energy to be 40 kJ, then your energy will remain 40 kJ in that frame.

Energy, momentum, etc. are just numbers. But the laws are consistent in every inertial frame.

ParadigmShift
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  • thanks for answer, could you please look at my comment above (well its below now)? – mirt Aug 14 '19 at 17:09
  • @mirt Maybe I understood that comment wrongly. please make it clearer. – ParadigmShift Aug 14 '19 at 17:37
  • Does energy–momentum relation (as defined in the beginning of https://en.wikipedia.org/wiki/Energy–momentum_relation ) meant to be used only in terms of stress-energy-momentum tensor but not with simple scalars? – mirt Aug 15 '19 at 12:34