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Entropy falling objects

  1. Sep 20, 2013 #1
    Dear sir,

    Hi, Everyone. I have a question about entropy. If the object falls without air resistant (vacuum system) , Is entropy changed? If ΔS=0, it means reversible, is it possible that the object can go back to the original height? I know that it is impossible but can we explain that ΔS >0.
    Within the condition as following:
    *** Focus on within the space (free falling under gravity)

    Thank you very much
    Sincerely,
     
  2. jcsd
  3. Sep 20, 2013 #2

    mfb

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    What do you think?

    Why? Assuming there are no other mechanisms where energy gets lost (inelastic collisions for example).
     
  4. Sep 20, 2013 #3

    The thing that I wonder is how can entropy increase while the object is falling in spite of no air resistant and no collision on the ground.
     
  5. Sep 20, 2013 #4

    mfb

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    That's my question: why do you think it would increase?
     
  6. Sep 20, 2013 #5
    ifΔs=0 it reversible, object is able to rise!!!! so i think that Δs>0
     
  7. Sep 20, 2013 #6

    mfb

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    Sure it is, and it will do so after a perfect elastic collision (or a frictionless U-shaped ramp).
     
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