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Homework Help: 2nd Law of Thermodynamics?

  1. Apr 15, 2009 #1
    I would apreciate some proof-readers giving their comments on my answer to an assignment for Undergrad Physics 2nd Year.

    1. The problem statement, all variables and given/known data

    Question: Give an explanation of the 2nd law to an intelegent non-scientific lay-person, drawing ideas from the K-P Statement, C's Statement and the Law of Increasing Entropy.

    2. Relevant equations


    3. The attempt at a solution


    Any comments (good or bad) would be very much apreciated, but please don't post revisions of any of my paragraphs, as I dont want to plagerise anyone elses ideas.

    Thank you everyone! :D
  2. jcsd
  3. Apr 15, 2009 #2


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    This is good, foxandthehen; the examples are familiar, and you've incorporated several implications of the Second Law, as required in the assignment. I have just a couple minor comments:

    - I strongly disagree with your statement that "...the second law of thermodynamics doesn’t look to tell us anything the average person doesn’t already know though observations of the world." I hope you, as a university physics student, don't really believe this; there are tons of non-intuitive implications of the Second Law (which either of us should be able to provide upon request). I think you might rephrase it to say instead that the Second Law explains many observations that the average person might make about the world.

    - Proofread, check your grammer (e.g., one of your essay's central ideas, "Area of high energy will naturally diffuse into areas of lower energy over time if allowed too," has a couple of errors), and choose your terms precisely (e.g., do hot objects become "cold," or would it be better to say that they cool to ambient temperature?).

    Be prepared for the occasional mischievous reader to ask you why oil and water don't stay mixed together. :smile:
  4. Apr 15, 2009 #3
    To start off... Thank you so much! and im 'sadly' dislexic and this is a first first draft (have only spend about 20mins on it), so I will be sitting down with someone to go through the grammar errors which MS word hasn't picked up, so thank you again for putting up with it!

    I did think about the oil and water example, but im hoping by putting it into the context of a cup of tea and milk, this becomes a consideration which is left to one side (wishful thinking perhaps as there is always one! :p)

    and as for the "...the Second Law of Thermodynamics doesn’t look to tell us anything the average person doesn’t already know though observations of the world." your so very right... now that I read it again and I'm thinking about how important the 2nd is outside of everyday observations and i will seriously revise that sentence!

    I am curious if anyone thinks I should be including more to do with the ideas of kenetic energy of single molecules and its transmitance, or if a lay-person would be very turned off by this idea, which altough is important, perhaps isnt in the contexts of this assignment?
  5. Apr 15, 2009 #4


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    I think somewhere you should state the law itself, and show how these examples fit with it, otherwise a person not familiar with it may think that the Second law of Thermodynamics deals exclusively with heat transfer when really it deals with Entropy (there can be entropy transfers w/o heat transfer, namely the entropy of mixing which you mention but may sound out of context in the sea of heat transfer examples).
  6. Apr 15, 2009 #5
    Hi! I once saw a list called something like 101 ways to express the second law of thermodynamics... so, I cant really state the law of thermodynamics because its accepted wording ranges from the law of increasing entropt, to the K-P statment, to C's statment, etc...

    or have i missed something?

    ps. we are asked not to be quoting the statements we used to build our explataion on as it needs to be an explation in our own words, not an explation of what the statements mean.
  7. Apr 15, 2009 #6


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    Well, then come up with your own. But I think it needs a statement that goes over all your examples. As you have it right now, it's somewhat like "example, example, example, example". Someone who hasn't heard of the second law before would have to find what those examples have in common, and that's not always easy.
  8. Apr 16, 2009 #7
    On second thoughs, good point! Perhpas I am taking the term lay-person a little to seriously when I have used examples to explain my final point! Thank you.
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