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Post by Vadim on Jun 27, 2008 22:54:51 GMT
Why don't I understand what's going on? What makes you think anyone else here does, Susan? Just bluff it. I should probably understand what's going on, especially as it's a parameter I use frequently! As for the rate of change of Jerk, this is undefined, but many take "jounce", and others make their own distinction. I suppose, to make it clear, one would call it "the rate of change of jerk". Maybe we should call it "Burk"?
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Post by Twoddle on Jun 27, 2008 23:06:23 GMT
What makes you think anyone else here does, Susan? Just bluff it. I should probably understand what's going on, especially as it's a parameter I use frequently! As for the rate of change of Jerk, this is undefined, but many take "jounce", and others make their own distinction. I suppose, to make it clear, one would call it "the rate of change of jerk". Maybe we should call it "Burk"? "Berk" is the original spelling, I think. Such an innocuous and mildly friendly word - almost a term of affection - until one examines its etymology.
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Post by Pete on Jun 28, 2008 0:32:24 GMT
Why don't I understand what's going on? Susan, a million (or so) years ago, I did maths at school and this is all about calculus, specifically the so-called differential calculus. To massively over-simplify it, if you plot your position against time, you get a line on a graph. If you measure the angle of slope of that line at any one point, what you are measuring is the rate of change of position, which is speed. And speed is called the first differential. So, suppose now you plot speed against time: now when you measure the slope of the line at any point, you have measured the rate of change of speed, which mathematicians call "acceleration". We non-mathematicians also call it "acceleration" but we also use "deceleration" when slowing down, whereas a mathematician will refer to the acceleration having a negative value. As you might have guessed, acceleration is the second differential. OK, if we plot acceleration against time, we can measure the slope of the line to find the rate of change of acceleration, which is the third differential and which has the name "jerk".
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Post by Pete on Jun 28, 2008 0:37:40 GMT
To continue the story, if you are travelling at a constant speed, you are not aware of any movement except through visual clues. Think of driving at a constant speed on the motorway at night - without the constant sight of passing objects, you don't feel as if you are moving.
When you are accelerating, you feel yourself being pushed back in your seat, so you are aware of a rate of change of speed. Now think about what happens with an inexperienced driver whose the gear changes are rather clunky. What you get is a noticeable change in the rate of acceleration, or a jerk.
And that's why it is called a jerk.
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Post by TfS on Jun 28, 2008 8:30:26 GMT
Now we have a second God amongst us. Congratulations on your elevation, Pete, which no doubt enabled you to confirm your status by the detailed explanation of acceleration. TfS
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Post by Pete on Jun 28, 2008 8:42:11 GMT
Now we have a second God amongst us. Congratulations on your elevation, Pete, which no doubt enabled you to confirm your status by the detailed explanation of acceleration. TfS Thank you, kind sir. We gods invented the laws of physics, of course, so we can explain them! ;D
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Post by TfS on Jun 28, 2008 9:10:55 GMT
Thank you, kind sir. We gods invented the laws of physics, of course, so we can explain them! ;D Indubitably so.
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Post by Twoddle on Jun 28, 2008 10:15:54 GMT
I'm faced with a problem now. As more members become gods, will I have to stop believing that they're real? Eventually, when I reach that lofty height, will I have to deny my own existence?
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Post by SusanB on Jun 28, 2008 14:49:45 GMT
Pete-God, thanks for your detailed explanation. It certainly helped me to understand why I was confused! (And I will read back over your explanation in an attempt to more completely unconfuse myself.) Twoddle, your advice to bluff it was equally sound, I think! Susan.
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Post by Barry on Jun 28, 2008 15:24:32 GMT
Nah, just think Olympus, Twod. Eventually, there'll be a bunch of posters with god status; it's then just a matter of division of labour (baggsy God of Tea).
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Post by SusanB on Jun 28, 2008 15:31:29 GMT
If I get there, I'd like god of curtains (drapes).
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Post by Dave on Jun 28, 2008 16:53:33 GMT
If I get there, I'd like god of curtains (drapes). "Then it's curtains for you, sister!"
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Post by Vadim on Jun 28, 2008 17:27:47 GMT
If I get there, I'd like god of curtains (drapes). "Then it's curtains for you, sister!" HaHa! Dave. Very good, if somewhat lame! I'm all for God of Emoticons ;D, when I get promoted from leader of the Autobots that is. PS. Thanks for the easy-to-understand explanation, Pete. I don't think the link I posted helped the fundamental understanding. I will try harder next time! (Why does it seem very obvious and simple to me, yet you "God-likes" on here, struggle with a simple differential?)
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Post by Pete on Jun 28, 2008 17:42:18 GMT
PS. Thanks for the easy-to-understand explanation, Pete. I don't think the link I posted helped the fundamental understanding. I will try harder next time! (Why does it seem very obvious and simple to me, yet you "God-likes" on here, struggle with a simple differential?) Perhaps because so many of us are verbivores*, not scientists or mathematicians? But I had a scientific upbringing, only switching to law in my late 20s. * Verbivore, forgive me but this is a perfect word for what we do here, methinks. And using the word generically is intended as a compliment.
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Post by Bertie on Jun 28, 2008 19:37:25 GMT
A very lucid explanation by Pete. I would be grateful if he could expand it to explain the phenomenon whereby when travelling on the highway at a constant speed, which is slightly higher than another vehicle also travelling at a constant speed, the rate of drawing away from that vehicle is - or appears to be - faster than that when closing the gap. I understand the concept in my mind, but have been unable to transmit it to others.
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