Experiments

July 19, 2004 4:07 PM

Hey Tommy, if a spring is bound and dropped into a vat of acid which dissolves it instantly, what happens to the spring's potential energy?

(If you haven't seen the comic before, you should start at the beginning.)
posted by Tlogmer to science & nature (16 comments total)

How could it possibly be dissolved instantly?
posted by kenko at 4:27 PM on July 19, 2004

If you bind the spring, fly it into outer space (~0 gravity), and then unbind it, what would happen?
posted by falconred at 4:41 PM on July 19, 2004

Doesn't acid give off heat as it corrodes? Also, either the binding or the spring would have to weaken to the point of giving way before it would completly dissolve, and release some of the energy. I would guess, anyway,
posted by Hackworth at 5:00 PM on July 19, 2004

falconred, what does gravity have to do with a bound spring's potential energy?

If you don't want to use the acid example, what if a bound spring at ground zero was disintegrated in a nuclear blast?
posted by riffola at 5:10 PM on July 19, 2004

The sizzling and heat would increase depeding on the amount of energy in what's being dissolved. It won't be noticeable as the potential energy is probably not as great as you think.

The same for a nuclear blast, there would be a difference but unmeasurable.
posted by geoff. at 5:15 PM on July 19, 2004

There is stress in the metal of the spring, so as bits come off they'll get propelled. The metal ions in the water will move slightly faster than they would had the spring not been compressed. (On the macro level, this translates to a slightly higher temperature.)
posted by fvw at 5:19 PM on July 19, 2004

I am not a chemist but...

as I recall, a spring's potential energy is stored as chemical bonds ultimately. Any acid that dissolves it has to do more actual work to do so.

You can actually forget about the spring altogether and just ask what happens to all the binding energy in *anything* when it is dissolved by an acid: it is released as heat. (exothermic process)
posted by vacapinta at 5:24 PM on July 19, 2004

vacapinta gets a smiley face.
posted by caddis at 5:32 PM on July 19, 2004

By the way, I just finished "The Guy I Almost Was." What a great story (graphic novel, whatever). It gets you thinking.

Thank you Tlogmer.
posted by caddis at 5:50 PM on July 19, 2004

What vacapinta and fvw said, mostly. The acid bath will just get a little hotter.

Falconred, why can't a spring simply detension in micro-gravity? All that will happen is that the spring will heat up.
posted by bonehead at 7:08 PM on July 19, 2004

It's important to note that "instantly" has nothing to do with anything. The interaction is the same, chemically and physically, whether it happens in a picosecond or over a long weekend. If what you really want is that the spring dissolves before the binding, that's all you need to say.

Past that, vacapinta's take sounds right, with maybe an appendix by Hackworth: at some point between being dropped in the acid and dissolving completely, the spring will probably fracture into several pieces, each of which will boioioing a little bit.

And that comic was great.
posted by gleuschk at 7:30 PM on July 19, 2004

Yeah, "The Guy I Almost Was" is probably my favorite comic at e-sheep, which is saying a lot. (vacapinta and fvw both sound right to me; thanks.)
posted by Tlogmer at 7:37 PM on July 19, 2004

Tlogmer, I just read the whole thing: terrific! Thanks.
posted by CunningLinguist at 5:44 AM on July 20, 2004

The atom bomb idea brings up a new idea for a super-weapon: put millions of bound springs around the center of an atomic bomb! Just think of the potential energy that would be unleashed in the explosion!
posted by zsazsa at 6:14 AM on July 20, 2004

I dunno. There's something about spring-loaded nukes which just doesn't sound right.
posted by DrJohnEvans at 7:58 AM on July 20, 2004

Compared to any chemical reaction, let alone a nuclear one, there's really not much energy storage in a mechanical spring. Consider da Vinci's car. Even with two masive coil springs, the thing can go less than 100m. For an equivalent weight of gasoline (and an engine, of course), you could drive 100s of km. An equivalent mass of plutonium could take you to a significant fraction of lightspeed.
posted by bonehead at 8:33 AM on July 20, 2004