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United States24745 Posts
For those who didn't read the introductory entry, head over to http://www.teamliquid.net/blogs/viewblog.php?topic_id=79275
Last time the question of the week was:
Question 6
Fluids
Three icebergs float in bathtubs brim full with ice-cold water. Iceberg A has a big air bubble in it. Iceberg W has some unfrozen water in it. Iceberg S has a railroad spike frozen in it. When they melt, what will happen?
a) Only the water in S will spill over
b) The water in S will get lower and the water in A and W will stay exactly brim full
c) The water in A will stay brim full, the water in W will spill over, and the water in S will spill over
d) All will spill over
e) All stay exactly brim full
The answer is b (S-> lower water level, A,W no change). The first thing is to realize that a floating (solid) iceberg will not change the level of water as it melts. Now consider A. Picture the air bubble pushed up to the very top of the iceberg. If it popped, there would be no significant change to the iceberg. Consider W. Move the water hole down to the bottom of the iceberg. If the surface pops, the water exchanges freely with the iceberg and nothing happens. Finally move the spike S down to the bottom. If it breaks free, it drops down, but the iceberg is released of its load and floats up, lowering the water level. I would rate this 3/5 difficulty because it is confusing with several different twists on an already tricky concept.
SCC-Faust was the first to get the right answer, but I don't allow 7 year olds to win in this blog. kramus was the first to provide a reasonable explanation, except he took for granted that A and W would be unchanged (but nice explanation for S). MasterOfChaos provided the first full explanation.
Question 7
Heat
You are camped by a mountain lake. The smoke from your breakfast campfire goes up a ways and then spreads in a flat layer over the lake. After breakfast you are hiking to higher elevations (above the smoke). At those elevations, the temperature will probably be:
a) cooler
b) warmer
Make absolutely sure to explain why you think this! Please use spoilers.
 
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cooler or warmer than what?
A. It's temperature assuming the campfire had not been lit
B. The temperature as compared to the temperature below the smoke
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United States24745 Posts
On October 28 2008 07:44 Chariot wrote:
cooler or warmer than what?
Than the temperature at ground level.
edit: spoilers please ._.
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Germany2896 Posts
+ Show Spoiler +The smoke moves up as long as the air carrying the smoke is warmer that the surrounding air. As it stops a bit up this means the temperature of the surounding air is warmer at that height. If I remember correctly it has a fancy name like "Inversion". edit: http://en.wikipedia.org/wiki/Temperature_inversionedit2: Forgot the letter. b) warmer
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United States24745 Posts
On October 28 2008 07:48 MasterOfChaos wrote:+ Show Spoiler +The smoke moves up as long as the air carrying the smoke is warmer that the surrounding air. As it stops a bit up this means the temperature of the surounding air is warmer at that height. If I remember correctly it has a fancy name like "Inversion". edit: http://en.wikipedia.org/wiki/Temperature_inversion
+ Show Spoiler +Indeed. I had an interesting story about that... a professor of physics who specialized in music (acoustician) lived a little over a mile from the campus he worked at. His neighbors were used to him listening to loud music.
On day they call him and tell him to turn down his music. He was wondering wth it could have been since his music was off... but then he realized there had been an evening temperature inversion, and the sound waves from a concert on campus were being directed back down towards the ground, and arrived at his community with high intensity.
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+ Show Spoiler +
Well the obvious answer is that the temperature above is cooler, since air thins at higher altitude. Most climbers know this.
However heat usually rises... but the smoke from your campfire did not. That implies that the air above is warmer than the air below.
Some strange thermal currents must be creating warm air at higher temperature, so in this special case my answer has to be b) warmer.
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Um I must be missing something. + Show Spoiler +I mean everybody who's gone hiking knows that it's colder high up in the mountains than it is at the base, but I don't see what what that has to do with the smoke?
edit: OK I get it now.
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+ Show Spoiler +
I think warmer, since if it's colder it'll make sense for the smoke to continue to rise above that level as well because the smoke would still be at lower density. instead of going flat
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+ Show Spoiler +The smoke from the fire moves upwards as long as the air near the smoke is warmer then the surrounding air. Which mean's the air is warmer at a specific height which is generally going to be somewhere higher.
Therefore it's B) Warmer.
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Don't even get me started on your grammar OP.
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United States24745 Posts
On October 28 2008 09:36 nAi.PrOtOsS wrote:
Don't even get me started on your grammar OP.
Lol what? Revenge for a comment I made earlier? Although I don't see anything wrong with the grammar..
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On October 28 2008 09:40 micronesia wrote:Show nested quote +On October 28 2008 09:36 nAi.PrOtOsS wrote:
Don't even get me started on your grammar OP. Lol what? Revenge for a comment I made earlier? Although I don't see anything wrong with the grammar..
No revenge, it is just difficult to follow with bad grammar. I am just giving you some good advice no bm meant.
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United States24745 Posts
On October 28 2008 09:43 nAi.PrOtOsS wrote:Show nested quote +On October 28 2008 09:40 micronesia wrote:On October 28 2008 09:36 nAi.PrOtOsS wrote:
Don't even get me started on your grammar OP. Lol what? Revenge for a comment I made earlier? Although I don't see anything wrong with the grammar.. No revenge, it is just difficult to follow with bad grammar. I am just giving you some good advice no bm meant.
I guess this is funnier since there are no grammar mistakes. But keep in mind, I'm not actually one of the ones who brought up your poor grammar ._.
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EPT
