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King_Ghidra
06-10-2005, 15:15:44
During a visit to the mental asylum, a visitor asked the Director what the criterion was which defined whether or not a patient should be institutionalized.


"Well," said the Director, "we fill up a bathtub, and then we offer a teaspoon, a teacup and a bucket to the patient and ask him or her to empty the bathtub."


"Oh, I understand," said the visitor. "A normal person would use the bucket because it's bigger than the spoon or the teacup."


"No." said the Director, "A normal person would pull the plug. Do you want a room with or without a view?"

King_Ghidra
06-10-2005, 15:16:09
:lol: i made a freudian slip on the thread title

novacane
06-10-2005, 15:20:38
You tease. I prefer inanity to insanity.

Funko
06-10-2005, 15:23:32
:lol: good joke.

novacane
06-10-2005, 15:25:46
At risk of taking this seriously.........

If there was no plug, I still wouldn't choose the bucket. You'd never EMPTY it with a bucket. Teacup is best.

Funko
06-10-2005, 15:27:22
I'd say, "get rid of your own dirty water you lazy bastard"

Tizzy
06-10-2005, 15:29:18
Originally posted by novacane
You'd never EMPTY it with a bucket.

Why?

Funko
06-10-2005, 15:29:54
He means because when you get near the end the bucket won't be able to collect the last little bits of water.

It's a good point, I like his logic.

Funko
06-10-2005, 15:30:38
I would use the bucket and get it nearly empty then go and do something else and let the last bit evaporate.

King_Ghidra
06-10-2005, 15:31:22
Originally posted by Funko
He means because when you get near the end the bucket won't be able to collect the last little bits of water.

It's a good point, I like his logic.

it is a disturbingly clever observation

novacane
06-10-2005, 15:31:41
Its too big. It wouldn't be able to scoop up all the water. Believe me, I was there for hours trying to empty the bath with that bucket last night. Then Gramercy came in with a cup of tea and I was like..............

:gotit:

Funko
06-10-2005, 15:32:02
:lol:

Tizzy
06-10-2005, 15:32:42
Oh yeah, good point.

Funko
06-10-2005, 15:33:33
In all fairness, the lazy option would be to not do anything and eventually the water would evaporate on it's own.

Another clear proof of the "if you do nothing you'll achieve as much as if you do something" principle.

novacane
06-10-2005, 15:35:21
How long would it take for a bath tub of water to evaporate. Out of interest. Got an equation?

Standard bath tub (?) - I guess..........8 months (in UK climate)

King_Ghidra
06-10-2005, 15:36:02
Originally posted by novacane
Its too big. Believe me, I was there for hours last night. Then Gramercy came.

MoSe
06-10-2005, 15:41:01
couldn't you suck it out to get rid of the last drips?

Tizzy
06-10-2005, 15:42:51
:lol:

Funko
06-10-2005, 15:42:53
You know if you leave water in a glass you can see the next day how much has evaporated...

1cm a day maybe? What's the depth of a normal bath (without a person) 50cm deep?

50 days? just over 7 weeks. ish.

novacane
06-10-2005, 15:43:03
Fucking hell MoSe. :lol:

I think thats the best x-post I've ever seen.

Funko
06-10-2005, 15:43:21
MoSe's post is particularly disturbing after K_G's

Funko
06-10-2005, 15:45:28
I think it might be the best x-post ever.

MoSe
06-10-2005, 15:46:46
Originally posted by novacane
the best x-post
:cute:


at the risk of ruining the fun....
..it was *construed as* an X-post

:cute:

Tizzy
06-10-2005, 15:47:59
Originally posted by Funko
I think it might be the best x-post ever.

That's what I was :lol: at

MoSe
06-10-2005, 15:50:42
OMG, I'm actually LOLling at my own post. I must hide in the loos!

Drekkus
06-10-2005, 15:51:31
That was an xpost?

MoSe
06-10-2005, 15:52:52
it would't be a driplet as funny if it couldn't be read as one

fp
06-10-2005, 16:18:49
Originally posted by Funko
You know if you leave water in a glass you can see the next day how much has evaporated...

1cm a day maybe? What's the depth of a normal bath (without a person) 50cm deep?

50 days? just over 7 weeks. ish.

Yeah that's right, because the 1cm depth in a glass of water is the same volume as 1cm depth in a bath...

You're banned from the geek forum for 10 days as penance for this flagrant Bad Science.

Funko
06-10-2005, 16:19:14
No, it is the same.

Funko
06-10-2005, 16:21:57
Given the same atmospheric conditions the same volume of water evaporates per unit surface area in the same time. So it doesn't matter what the surface area is, the same depth of water will evaporate in the same time, in the same environment.

novacane
06-10-2005, 16:24:36
I say 3 months now. I have vague recollections of a primary school experiment with a petri dish of water. I'm sure that took a couple of weeks to disappear.

Funko
06-10-2005, 16:25:12
Doesn't time go quickly...

Chris
06-10-2005, 16:25:32
Damn science geek.

Funko
06-10-2005, 16:25:44
ps. Can I do that pwned thing on fp now?

Chris
06-10-2005, 16:26:49
Why not? everybody else does.

fp
06-10-2005, 16:27:02
:nervous:

Funko
06-10-2005, 16:27:23
It's ok, I don't really know how to do it, I'd look silly.

novacane
06-10-2005, 16:27:47
Originally posted by Funko
Doesn't time go quickly...

Like watching water evaporate.

Funko
06-10-2005, 16:27:51
Tizzy - no comments on my last post please.

Chris
06-10-2005, 16:28:00
Never stopped you before.

Tizzy
06-10-2005, 16:30:45
Originally posted by Funko
Tizzy - no comments on my last post please.

Damnit, you know me too well :lol:

KrazyHorse
07-10-2005, 15:10:18
Originally posted by Funko
You know if you leave water in a glass you can see the next day how much has evaporated...

1cm a day maybe? What's the depth of a normal bath (without a person) 50cm deep?

50 days? just over 7 weeks. ish.

http://www.grow.arizona.edu/images/water/panevap.gif

My guess is that much of the UK is similar to New England or the Pacific Northwest, so 30 inches a year or so.

The average tub is probably close to 18-20 inches, so the initial guess in this thread of 8 months is surprisingly close.

Nills Lagerbaak
07-10-2005, 15:21:50
Originally posted by novacane
Its too big. It wouldn't be able to scoop up all the water. Believe me, I was there for hours trying to empty the bath with that bucket last night. Then Gramercy came in with a cup of tea and I was like..............

:gotit:


Hmm, I;m assuming having finished bathing and trying to empty the bath, you were still naked when Gramercy came in.
Or worse still, was Gramercy supposed to make a brew and join you IN the bath.

Pass me that bucket - I want to puke!

Funko
07-10-2005, 15:22:30
We don't get as cold as New England in winter, much milder all year round. But anyway a bath is indoors so there's no cooling at night.

An accidental experiment at home shows it does seem to be about a centimeter a day at room temperature indoors.

50cm is 20 inches. But thinking about it even if a tub is 20 inches deep, you don't fill it to the top and about half the volume is filled with person not water.

Google says the rate is about 40 g/m2/hr at 20 degrees c.

With the data that 1L of water weighs 1Kg and 1000 Litres is one cubic meter we can work it out...

Funko
07-10-2005, 15:23:21
or someone can, my brain isn't working.

novacane
07-10-2005, 15:27:02
Originally posted by KrazyHorse
The average tub is probably close to 18-20 inches, so the initial guess in this thread of 8 months is surprisingly close.

Surprisingly close?

My intelliegence is oft underestimated :p

Funko
07-10-2005, 15:27:26
thank goodness you aren't as stupid as you look.

novacane
07-10-2005, 15:28:54
Originally posted by Nills Lagerbaak
Hmm, I;m assuming having finished bathing and trying to empty the bath, you were still naked when Gramercy came in.
Or worse still, was Gramercy supposed to make a brew and join you IN the bath.

Pass me that bucket - I want to puke!

and as for you.............

Your homo-erotic brain is working overtime. You should get together with funko to chew the homo-erotic fat.

I've seen THAT picture.

Nills Lagerbaak
07-10-2005, 15:29:58
mmmm, homo-erotic fat. *Drooools*

Funko
07-10-2005, 15:31:06
It's brilliant for roast potatoes.

Funko
07-10-2005, 15:42:31
ok...

Take an area of water of surface area A and depth d

We know that in 1 hour 1 m^2 loses 40 grams of water. Which is 40 ml, which is 0.0004 m^3

The depth it loses in that time will be 0.0004 m = 0.04 cm?

So in 24 hours you lose 0.96cm depth of water?

Wow, how fucking close was I with 1cm a day?

:beer:

Funko
07-10-2005, 15:44:55
Or, I'm an order of magnitude out. Hang on a sec. :cute:

Immortal Wombat
07-10-2005, 15:45:56
or two

novacane
07-10-2005, 15:48:08
8 months.

novacane
07-10-2005, 15:49:25
or 3 months

Immortal Wombat
07-10-2005, 15:50:09
or 17 months

Nills Lagerbaak
07-10-2005, 15:52:27
Originally posted by Funko
ok...

Take an area of water of surface area A and depth d

We know that in 1 hour 1 m^2 loses 40 grams of water. Which is 40 ml, which is 0.0004 m^3

The depth it loses in that time will be 0.0004 m = 0.04 cm?

So in 24 hours you lose 0.96cm depth of water?

Wow, how fucking close was I with 1cm a day?

:beer:

Wait a minute. We know that we lose 0.0004m^3 in 1 hour.

but A*d(evap) = 0.0004m^3
d(evap) = 0.0004m^3/A


Did you intentially forget about d (evap)??

novacane
07-10-2005, 15:54:01
Surely if 1 m^2 loses 40 grams of water. Which is 40 ml, which is 0.0004 m^3 and ^9.6=3.3333333 then 1 cubic metre of water in 19.9%h will be the equivalent of H20^666/1

and you need to take into account d(evap)

No?

Nills Lagerbaak
07-10-2005, 15:56:55
666/1 ?? either evil or stupid.

Funko
07-10-2005, 15:58:37
d(evap) = 0.0004m^3/A

And I was using A = 1m^2

0.0004/1 = 0.0004

But I think that actually 40g of water is 40/1000 = 0.004 kg

and as 1kg = 1l that's 0.004 l

and 1000 l in a m^3 so it's

0.004/1000 = 0.00004 m^3

So you actually only get .096cm a day, which seems ridiculously low.

Funko
07-10-2005, 15:59:57
40 g/m^2/hour means it'd take 520 days to evaporate - so I don't believe the 40g/m^2/hour figure.

novacane
07-10-2005, 16:01:57
It would take a long time (>3 months) for a bathtub of water to evaporate(filled for use, not to the top, with nobody in it). You don't need science to know that.

I don't think 520 days is that unfeasible.

Nills Lagerbaak
07-10-2005, 16:02:10
Hmm, and assuming 1m^3 loses 40g of water an hour assumes rate of evaporation from a 1x1x1 cube....not very realstic in real bathing terms.

Evaporation = K*H1-H2 where H1 is the humidity of the water?! and H2 is the humidity of the air. and K is somekind of constant based on surface area ?!?

I don't really know but I think your model is too simple.

Funko
07-10-2005, 16:02:29
You corrected your post Nills, evil man.

d(evap) is what I'm calculating

Funko
07-10-2005, 16:03:23
Originally posted by Nills Lagerbaak
I don't really know but I think your model is too simple.

Of course it's simple, I'm a (lapsed) physicist not an engineer. :bash:

Funko
07-10-2005, 16:04:16
How do I tell Tizzy she can't have a shower for several months whilst I work out how long the bath takes to evaporate?

Nills Lagerbaak
07-10-2005, 16:04:52
ah, stop the press, I thought you said 1m^3 loses 40 ml water....never mind it all make sense now.

Where does the 40ml / m^2 come from? Surely it's a function of relative humidity and water temperature....

novacane
07-10-2005, 16:11:27
Originally posted by Funko
How do I tell Tizzy she can't have a shower for several months whilst I work out how long the bath takes to evaporate?

"You can't have a shower for several months whilst I work out how long the bath takes to evaporate. Lets make dirty love"

?

King_Ghidra
07-10-2005, 16:18:26
you're single huh

novacane
07-10-2005, 16:29:26
Yep :)

You're not :lol:

Nills Lagerbaak
07-10-2005, 16:34:53
Originally posted by Funko
You corrected your post Nills, evil man.

d(evap) is what I'm calculating


Right, I've cracked it. 2.5 cm / day.


1000Kg = 1 m^3

Therefore 0.04Kg (40 g) = 1/40 m^3

In a 1m^2 tube, rate of evaportation = 0.025m

Funko
07-10-2005, 16:37:50
I like that a lot. :beer:

So a mere 20 days.

novacane
07-10-2005, 16:38:09
Thats bollocks

MoSe
07-10-2005, 16:45:38
Originally posted by Funko
d(evap) = 0.0004m^3/A

And I was using A = 1m^2

0.0004/1 = 0.0004

But I think that actually 40g of water is 40/1000 = 0.004 kg [NO!]

and as 1kg = 1l that's 0.004 l

and 1000 l in a m^3 so it's

0.004/1000 = 0.00004 m^3 [0.004/1000=0.000004 !!! wrong start + WRONG CALCULATION => correct result! :lol:]

So you actually only get .096cm a day, which seems ridiculously low.


:clueless:

byp:
1kg=1000g
1g=0.001kg
40g=0.040kg

DO'H

1kg=1l=1dm^3=0.001m^3
.04kg=.04l=.04dm^3=0.00004m^3

you forgot a zero the first time, how many posts did it take you to notice?
advanced physics and a primary school unit conversion fault... :p

Immortal Wombat
07-10-2005, 16:46:46
1000Kg = 1 m^3

Therefore 0.04Kg (40 g) = 1/25000 m^3

In a 1m^2 tube, rate of evaportation = 0.00004m/hour

so 50cm = 12500 hours = 520 days again.

Funko
07-10-2005, 16:47:33
The surface area doesn't matter, smaller surface area, less mass evaporates. It cancels - FACT

Nills Lagerbaak
07-10-2005, 16:57:45
Of course the surface area matters. I m^3 of water in a 10mm^2 tube will take forever to evaporate. Im^3 of water spread out over 10m^2 will take no time at all.

Chris
07-10-2005, 16:58:06
All that math crap sucks - FACT!

Funko
07-10-2005, 16:58:37
Surface area doesn't matter when all you care about is the depth that evaporates per day.

Nills Lagerbaak
07-10-2005, 17:01:08
Word.

MoSe
07-10-2005, 17:09:22
What Funko assumes is that you do NOT need to have a constant volume

0.1m^2 10cm deep will take the same time to evaporate as 10m^2 10cm deep - or - constant depth=>volume proportional to exposed area

the same way that one jug to the brim will take the same time as 100 identical jugs just lined on a shelf....

Funko
07-10-2005, 17:11:47
Correct. The mass of water that evaporates is proportional to surface area.

(that's assuming that you are ignoring the changes to humidity of the water evaporating...)

Nills Lagerbaak
07-10-2005, 17:12:59
No I appreicate that, but 10m^3 with 1m^2 surface area will take longer to evaporate (completely) than 10m^3 with a 10m^2 area.

Like 1 jug filled to the brim will take longer to evaporate than that jug poored between 100 jugs.....

I love maths:love: :heart::gotit: :love:

Funko
07-10-2005, 17:14:19
Yay. :beer: :love:

Nills Lagerbaak
07-10-2005, 17:17:42
Now let's introduce a temperature difference between the water (at the surface layer) and the air....say 80Degrees difference....

Funko
07-10-2005, 17:19:24
At 100 degrees the water will be boiling you twat. :)

Chris
07-10-2005, 17:21:52
When will this mad attempt to educate us end???

If I wanted to know anything, would I be at CG?

Nills Lagerbaak
07-10-2005, 17:22:02
So? It's still gonna behave in exactly the same way as before....

Just cos you can't handle bathing in a boiling bath.

Funko
07-10-2005, 17:23:09
It won't, boiling water by definition is turning to gas because of the heat not just by evaporation.

Nills Lagerbaak
07-10-2005, 17:24:37
Same process dude. It is a common misconception that water turning into gas only takes place at 100 degrees.


Water evaporating is nothing more than water turining into gas.

MoSe
07-10-2005, 17:25:02
Originally posted by Nills Lagerbaak
that jug poored between 100 jugs.....

nicely put!
:lol:

when you "poor" from a jug you are left with less, you are thus the "poorer"... :lol:

Funko
07-10-2005, 17:25:37
Bah, technically that is correct.

Fucktard. :bash:

Nills Lagerbaak
07-10-2005, 17:25:42
:D I thank you!

Nills Lagerbaak
07-10-2005, 17:26:04
To both points!

MoSe
07-10-2005, 17:26:56
that's interesting
http://www.lns.cornell.edu/spr/1999-06/msg0016831.html
http://van.hep.uiuc.edu/van/qa/section/States_of_Matter_and_Energy/Boiling_Evaporating_and_Condensing/20020828090243.htm
http://van.hep.uiuc.edu/van/qa/section/States_of_Matter_and_Energy/Boiling_Evaporating_and_Condensing/20020321122324.htm

Nills Lagerbaak
07-10-2005, 17:28:03
"A useful skill in approaching physics problems is to ask if the situation is fully specified before going about calculating the answer."

Meow!

Nills Lagerbaak
07-10-2005, 17:30:02
I think I once created a model for this. As soon as you have a temperature difference you get conduction and convection (one which helps to maintain the surface temp. of water) and the other which heats up the air.....it was a bitch.

Funko
07-10-2005, 17:30:56
Fuck that, stick to simple cases with idealised conditions.

Funko
07-10-2005, 17:31:25
Fluid dynamics = very hard

Nills Lagerbaak
07-10-2005, 17:31:40
You have no application in the real world.

Funko
07-10-2005, 17:32:55
But you come with an easy to use applicator.

MoSe
07-10-2005, 17:40:04
anyway, supposing what you call a "quasi-static" transition, that is the speed of the process can be considered slow enough to not influence the variables at hand (water cooling, air humidity increasing close to the surface, etc...)

at 20C in constant average conditions 40g=0.00004m^3 will evaporate from a surface of 1m^2 in an hour
Those 40g, represent a depth of 0.00004m under that 1m^2 surface
0.00004m = .04mm

.04 mm/h * 24h/day = .96mm/day (a bit less than 1mm a day)

that's 1041 days & 16h for 1m deep
that is 148.8 weeks

3 1/2 months for 10cm

:hmm:

time we good CG students run a worldwide firsthand experiment!!!

:D

LoD
07-10-2005, 20:43:11
Originally posted by Funko
But you come with an easy to use applicator.

i.e. a dildo?

Greg W
08-10-2005, 01:15:56
He cums with a dildo? Kinky.

Funko
10-10-2005, 13:44:08
A tampon.