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#1 2005-10-19 00:52:40

mathsyperson
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Registered: 2005-06-22
Posts: 4,900

The spring

This question appeared in an exam that I did a while ago and it has since sparked a great debate about what the right answer is. I won't influence you with what anyone else thinks, but what's your view on this?

A spring is compressed and shut tightly in a box so that it can't stretch back out again. The box is then filled with acid and the spring dissolves. Energy cannot be created or destroyed, so what happened to the energy that was stored in the compressed spring?


Why did the vector cross the road?
It wanted to be normal.

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#2 2005-10-19 02:52:46

insomnia
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Registered: 2005-03-23
Posts: 944

Re: The spring

The energy that the spring held was potential energy. So, theorotically the spring didn't actually have any energy just the potential to transfer to kinetic energy. Just like a diver going to a high diving board. He gains potential energy but doesn't actually gain any energy.

I think that's right, but one part of my mind is telling me that potential is actually energy and the above is a totally wrong.


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#3 2005-10-19 02:57:30

mathsyperson
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Registered: 2005-06-22
Posts: 4,900

Re: The spring

I think that part of your mind is right. When a diver goes up to a diving board he uses energy while he is climbing, but gains it back as potential. He can then jump off to convert the potential back into kinetic and go WHEEEEEE, SPLASH, OWW, BELLY FLOP!!!


Why did the vector cross the road?
It wanted to be normal.

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#4 2005-10-19 09:54:41

MathsIsFun
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Registered: 2005-01-21
Posts: 7,529

Re: The spring

Did anyone open the box afterwards? Maybe a coil of acid jumped out!

OK: imagine the box was clear glass and you did a time-lapse video of the dissolving (or dissolution?)

At some point(s) you would see the spring getting weakened to the point where a crack develops. Then there would be a "jerk" of some sort as the spring released some of that energy.

So I guess it is much like "where does the energy of an earthquake go?" - In this case I guess it mostly gets transferred as motion (stirring up the acid) and sound ("crack!"), all of which then leaks out into the general world as friction.


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#5 2005-10-20 03:23:16

mathsyperson
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Registered: 2005-06-22
Posts: 4,900

Re: The spring

Thankyou! Finally someone agrees! That's exactly what I said, but everyone else thought that for some inexplicable reason more heat and sound and whatever would be given off as a result of it dissolving, just because it's compressed. But, yes. I also think that it would eventually get weak enough to snap itself.

Next great debate: Who would win out of ninjas and pirates?


Why did the vector cross the road?
It wanted to be normal.

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#6 2005-10-20 05:06:10

Zach
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Registered: 2005-03-23
Posts: 2,075

Re: The spring

Pirate. Pirates have pirate crews, boats AND booty (Especially females ones).

Plus, they have three point hats and cutlasses.

And it's common knowledge, that ninjas cannot swim.


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

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#7 2005-10-20 05:08:04

Zach
Member
Registered: 2005-03-23
Posts: 2,075

Re: The spring

Also, as the acid is eating away at the spring in the glass box, otherwise the acid would corrode the box, the energy would diffuse as heat energy, I'd expect.

Otherwise, the potential energy will diffuse into the acids own potential energy and form super potential.


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

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