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Post by Paul Doherty on Jul 25, 2008 13:40:00 GMT
In other words, the effect, the resultant movement, is due to a single force, the resultant of all the other forces in the system being considered That's the bit I don't agree with! I'm not trying to prolong this out of obstinacy or in an attempt to get you to change your mind -- I'm genuinely interested in why we see it differently. I wondered whether it's just a difference in wording, and that we actually agree, but it doesn't seem to be that. This is one of those times when I wish we could meet face-to-face -- it would make a fascinating pub discussion!
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Post by Paul Doherty on Jul 25, 2008 13:55:20 GMT
Tides are created by the moon and sun's gravitational pulls on the oceans ... the moon's and sun's gravitational pulls ... any consensus on which of the above variants is better Does it have to one of those? If so, I go for the latter, because the first is confusing: "moon and sun's" sounds like a joint thing, so then "pulls" surprises. The second is still clumsy, though.
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Post by Verbivore on Jul 25, 2008 14:16:52 GMT
[...] Does it have to one of those? Yes, unless one is recasting. Agreed - on both counts.
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Post by Dave M on Jul 25, 2008 15:55:55 GMT
That's the bit I don't agree with!
Nor I: there's a single movement only because a thing can't go in two directions at once, and we can say the movement is that which would result from a single force, but it's two forces which work together to produce that single "resultant".
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Post by Tone on Jul 25, 2008 21:02:50 GMT
"Pull s" -- people bogged down in the detail. "Pull" -- people who have the capacity to "see the big picture" (and the real world). Or, the difference between cause/s and effect! Tone
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Post by Geoff on Jul 26, 2008 0:13:54 GMT
That's the bit I don't agree with! Nor I: there's a single movement only because a thing can't go in two directions at once, and we can say the movement is that which would result from a single force, but it's two forces which work together to produce that single "resultant". That sounds to me to be exactly what I'm saying. In a system of forces acting on a body, if you resolve the forces (vectors) do you not end up with a single force (vector) that is the resultant of the other forces? This force is real, is it not, and doesn't the vector that represents this force define how and where the body moves? It is the force to which the body responds. As I've agreed before, there is no one thing that you can point to and say that it's the thing that is applying that force with that magnitude and in that direction. Therein lies our point of difference, I think.
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Post by Verbivore on Jul 26, 2008 6:58:17 GMT
This thread is growing to be more and more like an episode of Professor Julius Sumner Miller's "Why is it so" - a tv series from '60s/'70s Oz - except that the Professor answered questions just a tad more relevantly. www.abc.net.au/science/features/whyisitso/
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Post by Paul Doherty on Jul 26, 2008 10:10:49 GMT
This force is real, is it not No. there is no one thing that you can point to and say that it's the thing that is applying that force with that magnitude and in that direction. Exactly. Because it's not real. It's a mathematical fiction -- it's the imaginary force which would give the same effect as the real forces.
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Post by Pete on Jul 26, 2008 16:07:58 GMT
... a thing can't go in two directions at once ... It can but it's rare unless you are referring to sub-atomic particles. Photons do it all the time - tricky little buggers that they are!
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Post by Pete on Jul 26, 2008 16:13:28 GMT
In a system of forces acting on a body, if you resolve the forces (vectors) do you not end up with a single force (vector) that is the resultant of the other forces? This force is real, is it not, and doesn't the vector that represents this force define how and where the body moves? It is the force to which the body responds. I think this is where we differ. The body moves exactly as it would if there were a force acting on it that is equal to the resolution of the actual forces acting on it. But the body is not in fact moving due to such a force, as that force doesn't exist. The bosy is moving due to the actual forces acting on it. Putting it another way, one might say that the two gravitational forces combine to give a single scalar result but the fact is that there is no gravitational force of that magnitude and direction. There is only the scalar result of, in our example, two gravitational fields acting on a body of water.
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Post by Twoddle on Jul 26, 2008 17:11:07 GMT
In a system of forces acting on a body, if you resolve the forces (vectors) do you not end up with a single force (vector) that is the resultant of the other forces? This force is real, is it not, and doesn't the vector that represents this force define how and where the body moves? It is the force to which the body responds. I think this is where we differ. The body moves exactly as it would if there were a force acting on it that is equal to the resolution of the actual forces acting on it. But the body is not in fact moving due to such a force, as that force doesn't exist. The bosy is moving due to the actual forces acting on it. Putting it another way, one might say that the two gravitational forces combine to give a single scalar result but the fact is that there is no gravitational force of that magnitude and direction. There is only the scalar result of, in our example, two gravitational fields acting on a body of water. Obviously then, the solution is to reverse the polarity if the tachion particles, thus causing an increase in d-pi/p-pi bonding. God, why didn't I think of that before?! I'm so stupid at times!
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Post by Geoff on Jul 27, 2008 3:50:53 GMT
Paul,
If it's not real, but a mathematical fiction, then please explain why the body moves in accordance with a force having the same magnitude and direction as the vector that represents it.
Pete,
If the force doesn't exist, then the body wouldn't move (certainly not in accordance with the vector that represents that force).
Is this some form of new mathematics: resolving two forces (vectors, with magnitude and direction) produces a scalar quantity (non-vector, with only magnitude)? Sorry, I can't accept that. The sum of two or more vectors is itself a vector, even if the result is a null vector.
Paul et al,
Definitely my last word on this matter. I would hate to be discussing this face to face over a 'quiet' ale, because I don't think it would be too quiet. I'm going to stick to my guns on this one. Thanks for the opportunity to discuss, argue and debate the issue.
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Post by Paul Doherty on Jul 27, 2008 5:03:45 GMT
If it's not real, but a mathematical fiction, then please explain why the body moves in accordance with a force having the same magnitude and direction as the vector that represents it. Because the body is acted on by the forces that do exist! In the case of the barge, it's being dragged along by two ponies, one on either side of the canal. One double-pony walking on water would have the same effect on the barge, but there is no such pony.
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Post by Twoddle on Jul 27, 2008 10:03:43 GMT
If it's not real, but a mathematical fiction, then please explain why the body moves in accordance with a force having the same magnitude and direction as the vector that represents it. Because the body is acted on by the forces that do exist! In the case of the barge, it's being dragged along by two ponies, one on either side of the canal. One double-pony walking on water would have the same effect on the barge, but there is no such pony. Would the messianic pony have to have a halo?
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Post by Pete on Jul 27, 2008 11:01:03 GMT
Is this some form of new mathematics: resolving two forces (vectors, with magnitude and direction) produces a scalar quantity (non-vector, with only magnitude)? Sorry, I can't accept that. The sum of two or more vectors is itself a vector, even if the result is a null vector. Sorry, mea culpa. Got my terms mixed up. You are completely right that the sum of two vectors is another vector. The point I was trying to make is that the sum of two vectors of force does not equate to a third force of the saame type. The sum equates to a combined vector that "looks like" or "acts like" a third force with the combined vector but actually is not.
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