Modern Living

[Flyfisher]

I agree with Alice. I think the input energy would be released as mechanical energy as the torsion of the spring material is gradually released. I don't think the spring would need to return to its uncompressed length to release the original energy, it's the release of torsion along the length of the material that counts.

I think a similar thing might happen if a clamped compressed spring were heated. The heating would soften the material allowing the torsion to be released (= output of mechanical energy) so that when the clamp was released the spring would not return to its uncompressed length because there would be no more stored energy due to the release of the torsion.

But hopefully one of Alice's physics profs can settle it once and for all.

 

[NT]

I think tech progress is a dead cert unless we have world war 3. There is nothing other than total devastation and desperate poverty that can stop humankind being ingenious and developing new technology. And even amid desperation there are occasional advances.

There is also market progress, which has almost the same end result. To put it another way, there is a lot of already existing tech that isnt used because the marketplace will not safely support it at the moment. As material wealth continues to rise, many such techs will emerge onto the market.


Flyfisher:

So-called 'machine intelligence' might well be the saviour of humand-kind, who knows?

That in itself is an interesting question. CPU based machines have brought us great increase in wealth and been the saviour of a massive number of lives. I dont want to get totally offtrack into what computers may achieve in future, but I do think they will transform society in quite a big way, and will reshape human behaviour too, as their relationship with us becomes less one sided than it is today.

such unbridled optimism

Ooh. What I say is based on various facts & concepts that are quite soundly based, I'm not just reaching for the moon with a stick.

My concern about such unbridled optimism, though, is that it can reduce people's sense of responsibility to the point that they take none themselves. After all, why should anyone worry about their carbon footprint if they are optimistic that a technological solution (sequestration perhaps?) will be developed to solve the problem?

I'm sure anyone can act irresponsibly on any excuse they can imagine. I'm more interested in fact & logic than how many ways people can find to be foolish. If you wish to control mass behaviour, logical arguments dont seem to make as much much difference as idea marketing campaigns, fact doesnt seem to stop political agendas.

On a more pedantic point of detail about heat pumps breaking the 100% efficiency barrier; that, of course, is only true for a limited definition of 'efficiency'. As you well know, a heat pump supplements the electrical energy it consumes with environmental heat and the electrical energy is really just the 'harvesting cost'. You might as well argue that oil is more than 100% efficient because we get more energy from it than we put in to 'harvest' it.

It may well be possible to improve the efficiency of a heat pump in the future, but it won't, and can't exceed 100% efficiency in true energetic terms.

This is exactly the point I addressed in a previous post, where I explained that changing how one tackles a problem can have the same end result as increasing real efficiency to impossible levels.

Lets take another example, from the 1800s. Instead of trying to train telegraphists to key messages at superhuman speeds, a method was invented to transmit multiple messages simultaneously on one circuit. A new approach gave the same end result by bypassing what had seemed to be the barrier.

Unless, of course, we discover a new twist to the laws of physics and allow energy to be spontaneously created - how optimistic are you feeling?

That's already been done in the form of nuclear power. But the odds of such a thing being discovered again look about zero. While we dont know for sure, its got to be one of the planet's worst possible bets.


NT

 

[NT]

The Penners Pspring Problem is quite a brain bender. We could eliminate some false answers by saying assume the acid eats the spring at an even pace all over, so that no movement of the spring occurs as its eaten.

I'm going to wait for the prof's answer, as I cant profess to have an answer.


NT

 

[biffvernon]

Graham's right. It all ends up as heat. Most things do eventually. And heat, spread out evenly across the universe feels pretty cool.

 

[NT]

But at what stage does the mechanical force become heat, why and how?


NT

 

[Flyfisher]

Lets take another example, from the 1800s. Instead of trying to train telegraphists to key messages at superhuman speeds, a method was invented to transmit multiple messages simultaneously on one circuit. A new approach gave the same end result by bypassing what had seemed to be the barrier.

That's an example of increasing efficiency by using a different technique, which happens all the time, but it's not an example of exceeding 100% efficiency, which never happens (given our current understanding of the laws of physics).

Unless, of course, we discover a new twist to the laws of physics and allow energy to be spontaneously created - how optimistic are you feeling?

That's already been done in the form of nuclear power.

You're joking, of course?

 

[Flyfisher]

The Penners Pspring Problem is quite a brain bender. We could eliminate some false answers by saying assume the acid eats the spring at an even pace all over, so that no movement of the spring occurs as its eaten.

Why would an even erosion of the spring result in no movement? Even or uneven, I think it makes no difference. At some point, the reduced strength of the spring material would make it unable to retain the pent-up torsion (mechanical) energy and the material would move, releasing the original mechanical energy. I don't see that it matters if this happens simultaneously along the length of the spring material or in isolated sections over time.

I'm going to wait for the prof's answer, as I cant profess to have an answer.

Me too!

 

[Penners]

It all ends up as heat.

I wonder. Although I know nothing about such things, I wonder whether the answer lies somewhere in the bit of the law that I cheated by not quoting: the energy within a system can neither be created nor destroyed.

Does a single piece of coiled wire count as a system?

 

[Nigel Watts]

How about this as an explantion:

Molecules in a metal spring are held apart by electrostatic forces. In effect there is a little spring between each molecule and its adjacent partners. When the spring is compressed, these little springs are also compressed.

Heat manifests itself at the molecluar level in the form either of vibration of molecules (in a solid) or the speed of molecules whizzing around (in a gas or liquid).

As the compressed spring dissolves each molecule is freed from its neighbour. The more the electromagnetic spring was compressed, the gretear the velocity with which the freed molecule will voom off into the solution. The compressed spring with therefore increase the temperature of the liquid more than a uncompressed one, all else being equal.

 

[Penners]

In effect there is a little spring between each molecule and its adjacent partners. When the spring is compressed, these little springs are also compressed.

I'm not sure I agree with that, Nigel. I suggest that the molecules are not squeezed closer together, but rather that their arrangement/alignment is disturbed.

 

[NT]

Lets take another example, from the 1800s. Instead of trying to train telegraphists to key messages at superhuman speeds, a method was invented to transmit multiple messages simultaneously on one circuit. A new approach gave the same end result by bypassing what had seemed to be the barrier.

That's an example of increasing efficiency by using a different technique, which happens all the time, but it's not an example of exceeding 100% efficiency, which never happens (given our current understanding of the laws of physics).

Indeed. I get the feeling you might want to review the first post on this one.

Unless, of course, we discover a new twist to the laws of physics and allow energy to be spontaneously created - how optimistic are you feeling?

That's already been done in the form of nuclear power.

You're joking, of course?

Are you saying the ability to turn matter into energy has always been known? I didnt think Newtonian physics contained any provision for this.


NT

 

[NT]

In effect there is a little spring between each molecule and its adjacent partners. When the spring is compressed, these little springs are also compressed.

I'm not sure I agree with that, Nigel. I suggest that the molecules are not squeezed closer together, but rather that their arrangement/alignment is disturbed.

with some closer & some further apart, very slightly. If they simply flowed to take up their new positions, how would there be any spring force?


NT

 

[Penners]

In effect there is a little spring between each molecule and its adjacent partners. When the spring is compressed, these little springs are also compressed.

I'm not sure I agree with that, Nigel. I suggest that the molecules are not squeezed closer together, but rather that their arrangement/alignment is disturbed.

with some closer & some further apart, very slightly. If they simply flowed to take up their new positions, how would there be any spring force?

OK - I'll accept the slight variations in their proximities, but I didn't imply "flowing". The spring force surely comes from their wish to return to their natural alignment - the molecular structure that makes the steel steel.

 

[biffvernon]

Rather than talking of molecules it might be better to talk of distortions in the crystal lattices. The piezoelectric effect is a dramatic manifestation of energy release, in this case electrical, when a crystal is bent.

But whatever, it all ends up as so much heat.

 

[Flyfisher]

Unless, of course, we discover a new twist to the laws of physics and allow energy to be spontaneously created - how optimistic are you feeling?

That's already been done in the form of nuclear power.

You're joking, of course?

Are you saying the ability to turn matter into energy has always been known? I didnt think Newtonian physics contained any provision for this.

No, I'm saying you're wrong to suggest that allowing "energy to be spontaneously created" has "already been done in the form of nuclear power".

Nuclear power is just another method of energy conversion. When it was discovered by us is completely irrelevant.

 

[Penners]

it might be better to talk of distortions in the crystal lattices.

Fair enough!

 

[MdB]

Take a spring:

XXXX
XXXX
XXXX
XXXX
XXXX

and compress it:

xxxx
xxxx
xxxx
xxxx
xxxx

now start etching it from the middle.

xxxx
xxxX
xxx
xxxX
xxxx

note how as the etching progresses, molecules at the edge of the etching process go from the compressed state to the uncompresses state

xxxX
xxX
xx
xxX
xxxX

as each molecule uncompresses it will release its stored energy as heat

xxX
xX
x
xX
xxX

once the spring is etched through, all remaining stored energy will be released

XX
X

X
XX

Etching the spring all at once rather than just from the middle will work in a similar way (but is more difficult to show in a simple diagram)

 

[NT]

Unless, of course, we discover a new twist to the laws of physics and allow energy to be spontaneously created - how optimistic are you feeling?

You're joking, of course?

Are you saying the ability to turn matter into energy has always been known? I didnt think Newtonian physics contained any provision for this.

No, I'm saying you're wrong to suggest that allowing "energy to be spontaneously created" has "already been done in the form of nuclear power".

Nuclear power is just another method of energy conversion. When it was discovered by us is completely irrelevant.

Matter and energy are different things. Whatever the complexities below the surface, they are still different. Fission converts some matter to energy.


NT

 

[skier-hughes]

as each molecule uncompresses it will release its stored energy as heat

Was I actually right about something for a change?

Graham

 

[Mark]

can I recommend this

http://www.amazon.co.uk/Structures-Things-Dont-Fall-Down/dp/0306812835

A very good book on materials and structures in non-technical language.

Compression does move molecules closer rather than making them flow as long as the force keeps things within the elastic region. Hookes law etc.

your spring in acid will weaken until the spring material fractures at which point the energy comes out as mechanical energy. yes there will be heat/chemical energy as a consequence of the chemical reaction, but there will be plenty of mechanical energy going bang (or splash - dont stand too close)