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Author: Subject: Any physicists in the house? I promise I won't try to throw you out.
psychokinetic
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[*] posted on 5-9-2010 at 17:55
Any physicists in the house? I promise I won't try to throw you out.


I understand potential energy, and that energy input can be conserved as potential kinetic energy that can be released, and converted again once the object holding the energy reaches its target (say, lifting up and then releasing a football).

Now, when that football lands, has done its bouncy thang... what has happened to the energy? Has it all transferred to the surface it bounced on, and if so, in what form?

Liquids and gases are easy, as the energy pretty much gets transferred to other gaseous or liquid molecules.... but a solid isn't going anywhere o.o

Feel free to be a smartypants and tell me the answer, or to speculate/conspire. :)

[Edited on 6-9-2010 by psychokinetic]




“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
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watson.fawkes
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[*] posted on 5-9-2010 at 20:00


Quote: Originally posted by psychokinetic  
Now, when that football lands, has done its bouncy thang... what has happened to the energy? Has it all transferred to the surface it bounced on, and if so, in what form?
It's dissipated as heat through various kinds of friction and viscosity.
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Quantum_Dom
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[*] posted on 6-9-2010 at 11:16


Although your question might seem trivial to an everyday person, I can guarantee you that it is a very important one as it involves, as you said, one of the most fundamental law of physics: the conservation of energy. It is one of the few laws that applies at any physical scale; (sub)atomic, classical or cosmological. Without it, particle physics wouldnt be that advanced today and theyre wouldnt be a Large Hadron Collider, black holes would never have been detected etc... I can go very far with this.


Indeed, youre wondering "where did the energy go ?" as if somehow the energy transmited to the ball has simply dissapeared which is of course counterintuitive and, apparently, violates the very basic conservation principle you mentionned. Like Watson stated, the ground is constitute of solid material, the phase of the latter is simply due to the nature of the interactions of the atoms of the ground. So, once the ball hit the ground it transfers some of its energy to the "atoms of the ground" which is dissipate into the huge amount of degrees of freedom they have (translation, vibration ). This perturbation, would also transfer some of its energy to the air molecules all the way to your eardrums and it would be perceived as "sound" by you. So the ball, indirectly, would give some of its energy to you. ;) Some of the energy transfered by the ball would also be converted into heat, if you would actually be able to measure with high precision the temperature of the ground, you would see that the temperature would actually increase after the impact. I think you get the idea and always be skeptical when energy has, apparently, been created, or destroyed, out of the blue. ;)

QD

[Edited on 6-9-2010 by Quantum_Dom]




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Lambda-Eyde
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[*] posted on 6-9-2010 at 11:35


Quote: Originally posted by Quantum_Dom  
It is one of the few laws that applies at any physical scale; (sub)atomic, classical or cosmological.


http://www.scientificamerican.com/article.cfm?id=is-the-univ...
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Quantum_Dom
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[*] posted on 6-9-2010 at 11:47


Quote: Originally posted by Lambda-Eyde  
Quote: Originally posted by Quantum_Dom  
It is one of the few laws that applies at any physical scale; (sub)atomic, classical or cosmological.


http://www.scientificamerican.com/article.cfm?id=is-the-univ...


Nice ! Thanks for that :) Of course you do realize that this is an ad hoc statement and has yet to be proven untill the actual nature (open, close etc) of the universe is determined right ?

Nevertheless, Lambda-Eyde makes a very good point and an excellent addition to my previous post. Another fundamental principle of physics is that nothing is absolute and all, apparently irrefutable, laws can be challenged and revoked at some point. :cool:

QD

[Edited on 6-9-2010 by Quantum_Dom]




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psychokinetic
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[*] posted on 6-9-2010 at 12:54


Quote:
sound


*facepalm* Of course.

Thanks for your replies, guys. It really was having me stumped, but I suppose I was thinking too much on a "1 unit in, 1 unit out" train of thought.

This question came to me yesterday while waiting for the bus. I was considering the falling rain (and boy was a falling, my university was almost isolated by the creek that was trying to be a river), and the energy input required in getting it up in the sky in the first place (and where that came from, and where that came from.... ad nausea). Then I was considering the splashes, i.e. the continued kinetic energy. But I got to the gist of my question when I thought - where is the energy when the water finally settles? The water is still there, but the energy has moved on.

I suppose the fact that the energy has moved on also works for the almighty second law of thermodynamics. It's another 'chance' for energy to be input and used by that water.

Sometimes I think too much for my own good.




“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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peach
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[*] posted on 9-9-2010 at 11:35


Quote:
"1 unit in, 1 unit out"


Denying nature the respect it deserves for it's intricacies can be a dangerous thing.

{An example of oversimplification. The bridge is fine, under static loading. Load it at resonant frequency, using the vortexes the breeze is generating around it, and it goes ape shit. The guys who designed the Millennium bridge in London made precisely the same mistake, a long time on. This is such a common and important example, CAD software like Solid Works can now model how the structure will deform through the frequency spectrum, to look for resonance problems}


As the others say, it's heat and sound.




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Magpie
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[*] posted on 9-9-2010 at 13:29


Peach, that's Galloping Gertie in Washington State. For more of this story and a photo of the bridge collapsing see:

http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_%281940%2...




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peach
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[*] posted on 10-9-2010 at 02:58


Quote: Originally posted by Magpie  
Peach, that's Galloping Gertie in Washington State. For more of this story and a photo of the bridge collapsing see:

http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_%281940%2...


Thanks Magpie, I didn't really look for a specific example, just a photo of a bridge going wonky due to odd loading; apologies if that's not entirely fitting to the resonance chattering <---- a joke? :D I tried finding one of the Millennium bridge doing it, but I think they've all been censored by the government as part of a "cover up how stupid this makes us look" conspiracy scheme.

I was speaking to a guy who's dad helped build one of the famous bridges, the Golden Gate or something like that. He stole the plaque off it as a memento & compensation.




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