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mvenus9292913
Joined: 08 Jan 2007
Posts: 23
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 Posted: Tue May 01, 2007 7:26 pm Post subject: Question 49 |
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| Your explanation seems to indicate B is the correct answer (minimize area to volume ratio). Can you elaborate a little more in the explanation (I don't have GS books, so I can't look it up). |
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mcat_premed3832
Joined: 19 Oct 2006
Posts: 412
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| Posted: Wed May 02, 2007 5:39 pm Post subject: |
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| The sphere is a natural shape which has the minimal surface area for the maximal volume contained. This minimizes interaction with the environment and thus minimizes surface tension (answer choice A). Answer choice B says the opposite (it says maximizes area to volume). |
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mvenus9292913
Joined: 08 Jan 2007
Posts: 23
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| Posted: Fri May 04, 2007 11:22 pm Post subject: |
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| Heh heh... my bad. I just haven't been reading well lately. |
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admin
Site Admin
Joined: 08 Dec 2003
Posts: 2176
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| Posted: Sat May 05, 2007 12:23 am Post subject: |
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| No problem. When you are looking over an answer, before you move on to the next, always ask yourself: what did I do wrong? or what silly mistake did I just make? It just takes a few seconds but it will help you find something you may have missed. |
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mcat_premed3832
Joined: 19 Oct 2006
Posts: 412
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| Posted: Fri Jul 13, 2007 5:37 pm Post subject: |
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Question from yfangl097543:
If the droplets tend to be as small as possible, wouldn't that maximize the area-volume ratio, since larger droplets would have less surface area and more volume? Also, what does minimizing the surface tension do and why do the water droplets want to minimize it? Thanks! |
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admin
Site Admin
Joined: 08 Dec 2003
Posts: 2176
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| Posted: Fri Jul 13, 2007 6:24 pm Post subject: |
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From Wikipedia:
| Quote: | Beading of rain water on the surface of a waxed automobile.
Water adheres weakly to wax and strongly to itself, so water clusters in drops. Surface tension gives them their near-spherical shape, because a sphere has the smallest possible surface area to volume ratio. |
http://en.wikipedia.org/wiki/Surface_tension
Also, in terms of your question, the comparison in the problem is not between big and small drops, rather, it's about shape. Compared to other possible shapes, the sphere has the smallest surface area to volume ratio. This is why water takes this shape as drops or droplets http://physicsweb.org/articles/world/14/5/8 and it's why when you boil water, vapor forms in spheres which, of course, rise to the surface of the fluid because of the difference in density.
You may also find the following helpful:
http://www.newton.dep.anl.gov/askasci/phy00/phy00627.htm |
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terryheidt1382
Joined: 24 Apr 2010
Posts: 4
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| Posted: Sun Aug 15, 2010 11:51 am Post subject: |
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Is surface tension not a property of the liquid? Surface tension values are given based on temperature and composition of the liquid, not area exposed. In one of the links provided:
"The surface tension is determined by what molecules are present in the one or so layers of molecules at the surface of the interface between a liquid and its vapor or air from the atmosphere."
The force due to surface tension may be minimized but not the actual surface tension itself?
Cheers. |
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airdow547702
Joined: 29 Jun 2011
Posts: 2
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| Posted: Thu Jul 28, 2011 1:45 pm Post subject: |
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| This question definitely sounds like it is asking why water forms small drops opposed to large ones. The fact that it forms small drops makes it seem like it is trying to maximize area/volume because a large drop would have a smaller area/volume |
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