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Speed & gravity

  1. Aug 6, 2005 #1

    LeonhardEuler

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    In SR, when an object starts moving quickly, it seems to have more mass in the sense that it requires more force to accelerate it at a given rate. Dose the object also behave as if it has more mass in the sense that other objects are more attracted to it gravitationaly?
     
  2. jcsd
  3. Aug 6, 2005 #2

    JesseM

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    As jtbell points out in post #180 of this thread, it's not as simple as saying the object just behaves like it's more massive, because the force required to accelerate a moving object will depend on the direction of the force relative to the direction of motion--it's hardest to accelerate the object parallel to the direction of motion, but easier in other directions.
    This is discussed in this question from the Usenet Physics FAQ:
    This stuff was also discussed at length on this thread.
     
  4. Aug 6, 2005 #3

    LeonhardEuler

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    Thanks!oiasd
     
  5. Aug 6, 2005 #4

    pervect

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    You might also want to take a look at this thread where the issues has been discussed previously.
     
  6. Aug 6, 2005 #5

    Aer

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    This is a very good question for JesseM and Pervect to answer directly
    :biggrin:

    Go ahead.
     
  7. Aug 6, 2005 #6

    pervect

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    I already have, though I've rambled on a bit more than is necessary. One of these days I'll probably try to write a clearer summary with nice diagrams. Don't hold your breath waiting, though, you might turn blue :-).

    One of the things I really need to do before I write the summary is to sit down and investigate energy pseudo-tensors more, because I think they should provide the clearest answer to the quesiton (via an anology to Gauss's law).

    I think it's unfortunate that this question doesn't seem to be addressed more fully (with worked examples) in the literature or in the textbooks (at least the couple of textbooks I've looked at). MTW seems to treat everything else in detail, for instance (hence the size of the book :-)), but their treatment of this issue is downright skimpy.
     
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