Container and its contents

Discussion in 'Physics' started by logearav, Jan 17, 2012.

  1. logearav

    Thread Starter Member

    Aug 19, 2011
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    Revered Members,
    Recently i attended an interview and I am confronted with the following questions.
    1) Can you a fill a 10 litre container with air alone?
    2) Can you fill a 10 litre container with 15 litres of water?
    3) When you fill a 10 litre container with water full to the brim, does the container contain water alone or air mixed with it?
    I gave the following answers but i could not know if they are right or wrong, since i can't judge anything from the body language or facial expressions of interviewer
    My answers
    1) No, its not possible
    2) No. A 10 litre container can accommodate only 10 litres of water
    3) When i fill the container with water, the air gets displaced. So, the container contains water alone
    I require the help of the revered members to ascertain whether I am right or wrong.
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    1) Yes
    2) No
    3) Water and air
     
    logearav likes this.
  3. davebee

    Well-Known Member

    Oct 22, 2008
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    logearav, why do you say no to the first question?
     
  4. logearav

    Thread Starter Member

    Aug 19, 2011
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    davebee,
    I thought it is impossible to fill a container with air with its top end open .
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    We swim in an ocean of air. If you put a container underwater is it full of water?
     
  6. Georacer

    Moderator

    Nov 25, 2009
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    I 'd agree with logearav for q. #3.
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Does anyone know if water can be compressed by 1/3rd? It would take an unrealistically great deal of pressure, of course. But would there necessarily be a phase change in the process (from liquid to solid)? If not, then the answer to #2 would be yes.
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    1. YES, provided the definition of air includes "typical air" containing contaminants, which the most likely definition would include.

    2. YES, the process will fill the container and then any excess water will spill out and be wasted. After the process completes the 10 litre container will definitely be "filled".

    3. WATER+AIR, as a typical process of filling a container with water (pouring) there will be some air entrapped in the water due to the process. Even independently of the process, "water" as we know it almost always has some air trapped.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    All YES. Simple

    Water always carries air.
     
  10. Andreas

    Active Member

    Jan 26, 2009
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    1) Can you a fill a 10 litre container with air alone?
    Air contains many elements other than primarily Nitrogen, Oxygen, Argon and CO2. Water vapour (gas) also exists in various amounts.

    2) Can you fill a 10 litre container with 15 litres of water?
    Water behaves in strange ways compared to other liquids when exposed to pressures and temperatures beyond the norm. Then again a large flat tray used as your container might provide enough surface area to maintain enough surface tension to yield the extra volume. Ha.

    3) When you fill a 10 litre container with water full to the brim, does the container contain water alone or air mixed with it?
    If it didn't contain air then how would fish breathe?

    These questions are too open to conjecture and are the sort that make forum discussions go on and on and on and on... Was the interview for a job or for gaining entry into MENSA?
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I allowed for the surface tension (convex meniscus) argument but eliminated it as technically any water extending above the top edge of the container is not "in" the container, and this is further strengthened by the fact the container has a specified volume, as its volume would not include any volume above the top edge of the container (volume of 10 litres does not include any volume >10 litres).

    I think the logical argument is the best interpretation for question 2.
    You can't fill volume X with <X beans
    You can fill volume X with >=X beans (you just have leftover beans, a solution which is not excluded by the wording of the question).

    And I agree they look much more like IQ or "lateral thinking" questions than physics questions!
     
  12. Andreas

    Active Member

    Jan 26, 2009
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    Dear RB,

    I understand what you are saying and I like your logical analysis but you have contradicted yourself.
    The sentence reads: "Can you fill a 10 litre container with 15 litres of water? but there is no mention of "in", in the question. This is just your interpretation. If any excess water created by a meniscus is considered outside of the container and therefore breaks "your" rules then doesn't your overspilled water outside of the container also break "your" rules?

    In any case, the key word in the sentence is; "fill" which is in this case used as a verb. So I'd have to agree with you that it is possible to fill a 10L container with 15L of water and whatever happens to the rest of the water is nor here nor there, meniscus or no meniscus.....
     
  13. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    When thinking on the Air/Water one, just consider fish, and how they breathe (Dissolved air in the water).
     
  14. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I am a freakin Genius.:D
     
  15. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Not at all. The requirement to "fill" a volume specifies that volume, which is then achieved regardless of meniscus or spill. So in a "fill" solution the meniscus and container shape is irrelevant.

    By attempting a meniscus solution it looked as though you interpreted the question as "Can you put 15 litres of water in a 10 litre container?". In that case the answer is always no you can't put 15 litres IN 10 litres. Even with a trick like compressing the substance it is still no, as 15 litres compressed is no longer 15 litres. And likewise you can't "expand" the 10 litres as it would no longer be 10 litres. "Put B in A" is only true when B <= A.
     
  16. John P

    AAC Fanatic!

    Oct 14, 2008
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    I'm not entirely sure what the word "fill" in this thread means. Does it mean simply pour into, or does it mean the entire volume is occupied?

    Not that I've ever done it or seen it done, but I've heard there is a trick that sounds like question 2. There's a bucket placed so you can see it, but not what's in it. Someone comes in with another bucket, shows you that it's full of water, and pours it into the first one, stirring as they go. Then they bring in another bucket, half full of water, and they show it to you and pour that into the first bucket, and stir it. So what was in the magic bucket? The answer is "cement". As the water is added, a chemical reaction occurs which reduces the volume, so more water can be added. Whether it lets you add 150% of the volume, I don't know.

    I suppose in #1 and #3, there's a possibility that they want you to say that there's water in the air, and air in water. But then, "air" is a mixture of gases, one of which is water (in vapor form) so really, water isn't an impurity in air, it's a part of air. And filling a container with water alone--does that mean absolutely pure water? You might have to fill the container with absolutely pure water, and then boil it to get the dissolved air out, because there'll always be some. Perhaps that's what they wanted to hear.
     
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