Easy entropy problem, what is the permitted entropy?

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The discussion revolves around identifying five physically possible entropies and five that are not real, with participants noting they have only found four. A reference to Callen's textbook highlights the importance of considering violations of Postulate IV in this context. Participants discuss the implications of the relationship between entropy (S) and internal energy (U), particularly under certain conditions. There is confusion regarding the states where the derivative of U with respect to S equals zero, and whether these states imply S equals zero. The conversation emphasizes the complexity of entropy and its foundational principles in thermodynamics.
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Homework Statement
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Relevant Equations
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There is five physically possible entropy to exist, and five entropy which can't be real, find it all.

I could found just four entropy, what is the another?

B, H and J:
S(λU,λV,λN) ≠ λS(U,V,N)
D:
∂S/∂U < 0

what is the another?
(another or other??)
 
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This is a problem from Callen's textbook. Did you consider violations of Callen's Postulate IV?

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TSny said:
This is a problem from Callen's textbook. Did you consider violations of Callen's Postulate IV?

View attachment 267814
Actually i thought about it, since was the only postulate i not mentioned, however, i don't know how could i deal with this, since i don't have an equation in the options which leave me direct to the temperature.
I don't think we can say U = NfkT/2 as generally do for some cases.
 
From the functional form of each relation between S and U, you can consider if there are any states where $$\left( \frac{\partial U}{\partial S} \right)_{V, N} = 0$$
If there are such states, do these states satisfy ##S = 0##?
 
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TSny said:
From the functional form of each relation between S and U, you can consider if there are any states where $$\left( \frac{\partial U}{\partial S} \right)_{V, N} = 0$$
If there are such states, do these states satisfy ##S = 0##?
Oh, i was making a confusing zzz thx
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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