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View Diary: Weekly Physics: Equations of Motion (63 comments)

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  •  um well here's the thing (1+ / 0-)
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    Jim W

    the answer is no but there is a catch.

    See there's not just gravity you have to deal with, you have to deal with what is known as inertial frames of reference.

    This gets incredibly complicated (I was not introduced to this still junior year) but essentially you have to account for the fact that your frame of the reference (the earth) is itself moving.

    Now of course if you are not throwing your object very far or fast this is not too much of a factor. But for example if you were to launch artillery at a target you could be off substantially. Enough so that you could risk hitting things you would rather not.

    That said, back to your question, gravity is not strictly uniform, there are points on the earth where it is stronger and points where it is weaker. When you deal with the earth as a whole these facts don't matter. On the earth, mostly physicist assume (correctly) that the fluctuations are minor enough to be ignored.

    As for what your instructor is talking about, I hesitate to correct someone especially when I am unsure of what is being said. That said rotational motion is complicated and it may be that you misunderstood. Eventually I will get to centripetal acceleration and rotational motion.

    It's best not to think of things in terms of a power source though. The thing is the fundamental exchange that governs gravity is just not well understand. Gravity frankly should not be as weak as it is and it is frustrating to deal with. On a micro level gravity is so weak you can ignore it and yet it is so powerful on the macro scale that it dominates.

    A song about life
    Why aren't you more like Gandhi? Why aren't I?

    by drache on Sun Jun 07, 2009 at 10:56:39 PM PDT

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