• June 12, 2023, 3:05 p.m.

    Yes. Perhaps I should change what I said to 'Steering changes the speed of a car over and above the effect of not steering'.
    This is a process to which I've become well used. I start of with a statement which is true, given sensible assumptions. Someone makes a silly challenge to it, which is dealt with. Then other people chime in with edge cases, which are valid. So then I have to make the statement more precise to remove the assumptions which those edge cases depend on. The next step will be for me to be accused of over-complicating things.

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  • Members 509 posts
    June 13, 2023, 10:48 a.m.

    I suspect this problem is why physicists decided writing down physics in mathematical form rather than words was a good thing. Words always seem to open up possibilities for fudge, muddle and confusion no matter how hard you try. Lawyer language is almost incomprehensible because of the need to encompass every caveat.

  • June 13, 2023, 12:12 p.m.

    Exactly.

    And the problem here is that there is an active faction which wants to deny the actuality, for whatever reason - and they will pick away at any ambiguity and demand clarification, until the resultant text is very lawyerly.

  • Members 243 posts
    June 13, 2023, 1:13 p.m.

    I actually did not. That side of my brain is inoperative.

    I apply to the Oxford definition, or Miriam Webster, where acceleration is gaining speed and deceleration is to lose speed, while the physics definition is any change in speed. While I may be wrong, I can guarantee nobody involved with race cars see it from the physics definition.

  • June 13, 2023, 1:53 p.m.

    The 'physics' definition just accounts for the idea that just under half of the integers can be negative (or positive for that matter).

  • Members 138 posts
    June 13, 2023, 2:12 p.m.

    The so-called "physics definition" comes from the need to do math that corresponds to the phenomenon. Getting to space would not be possible without the math behind orbital mechanics and ballistics. In that vernacular, acceleration is not distinguished such in that, from state to state, so-called de-acceleration would probably be just a lesser positive number...

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    June 13, 2023, 2:31 p.m.
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    June 13, 2023, 4:19 p.m.

    [deleted]

  • Removed user
    June 13, 2023, 4:36 p.m.

    So, acceleration is not a vector?

  • edit

    Thread title has been changed from Photography Myth #1.

  • Members 138 posts
    June 13, 2023, 5:04 p.m.

    So, state is a three-valued vector that gives position in XYZ coordinates, velocity is the three-valued vector describing the relative motion observed on that state, and acceleration is a three-valued vector that describes the instantaneous change impinged upon that velocity. You iteratively integrate velocity with acceleration to produce a trajectory, which is a collection of states describing the object's anticipated path.

    In my old day job, we did a lot of this propagating missile trajectories. For a ballistic (no further energy) flyout, all three values of the acceleration vector was constant, 9.8 meters per second-squared, the pull of gravity...

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    June 13, 2023, 5:26 p.m.

    oops, thanks, been a while since I've done it...