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Author Topic: Which weighs more?  (Read 8328 times)

DoctorBeaver

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Which weighs more?
« on: 29/05/2007 12:28:22 »
A coil spring or the same spring under compression?

dentstudent

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Which weighs more?
« Reply #1 on: 29/05/2007 12:35:48 »
I think they have to weigh the same...there is no mass added or subtracted through compression - there is force added though, so if you have the spring on a set of bathroom scales, say, and push down, you would be measuring the additional downward force used by your hand to compress the spring as well as the weight of the spring itself, which is perhaps why it might look as though the spring weighs more. So, you'd be adding potential energy but no mass.

DoctorBeaver

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Which weighs more?
« Reply #2 on: 29/05/2007 12:42:50 »

Bored chemist

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Which weighs more?
« Reply #3 on: 29/05/2007 12:45:12 »
The coiled one by E=MC^2 but I chalenge you to demonstrate it.

Seany

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Which weighs more?
« Reply #4 on: 29/05/2007 13:10:38 »
Have fun outboffing everyone.

dentstudent

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Which weighs more?
« Reply #5 on: 29/05/2007 13:49:59 »
Clearly, I'm not a physicist so I welcome a duffers guide,  but does this mean that energy has some sort of quantum mass? So the spring's weight changes by the increase in potential energy? Perhaps I'm guessing wildly and should leave it to the experts!

DoctorBeaver

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Which weighs more?
« Reply #6 on: 29/05/2007 21:40:11 »
Our splendid BoredChemist has the right answer.

A coiled spring has more potential energy than an uncoiled 1. Therefore, for E=MC^2 to remain balanced, the righthand side of the equation must reflect an increase also. C cannot increase so the only answer is for M to increase.

(OK, I suppose I should've asked "Which has the most mass?")

The same holds true for a given volume of cold water & the same volume of cold water (or for anything weighed at different temperatures).

So, ladies, when you look at the scales when you weigh yourselves and go "AAAARRRRGH!", simply immerse yourself in a bath of cold water & hey presto, you will weigh less!

syhprum

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Which weighs more?
« Reply #7 on: 29/05/2007 22:54:16 »
I take it that if I cut the bond holding it in a compressed state so that it oscillates then it would radiate gravitational waves (also hard to demonstrate).

DoctorBeaver

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Which weighs more?
« Reply #8 on: 30/05/2007 11:47:26 »
I take it that if I cut the bond holding it in a compressed state so that it oscillates then it would radiate gravitational waves (also hard to demonstrate).

erm... well... er... oh gosh, is that the time? I've got to go  [:I]

Seany

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Which weighs more?
« Reply #9 on: 30/05/2007 12:36:40 »
Where to? Beaverland?

lightarrow

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Which weighs more?
« Reply #10 on: 30/05/2007 13:31:08 »
A coil spring or the same spring under compression?
Ok, now I ask you a question:
You compress a gas isothermically. Will it weigh more after compression?

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Which weighs more?
« Reply #10 on: 30/05/2007 13:31:08 »