# What is this conservation of energy

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 September 26, 2013, 03:22 What is this conservation of energy #1 New Member   Sayee chandrasekara mouli Join Date: Mar 2012 Posts: 21 Rep Power: 14 Im very bad in basics to understand here all fluids --> Bernoulli's equation we got P+1/2 v^2/2+rho*g*h Here instead of p can we insert Internal energy U as we do in First law of thermodynamics. If yes, then can we say that Internal energy can also be any energy acting inside a system (Microscopic and macroscopic). If no why is that?

September 26, 2013, 09:24
#2
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Filippo Maria Denaro
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Quote:
 Originally Posted by mouli1991 Im very bad in basics to understand here all fluids --> Bernoulli's equation we got P+1/2 v^2/2+rho*g*h Here instead of p can we insert Internal energy U as we do in First law of thermodynamics. If yes, then can we say that Internal energy can also be any energy acting inside a system (Microscopic and macroscopic). If no why is that?
Sorry, could you state your question in a more clear way?

Bernouilli is valid only for fluid of constant density and in absence of any dissipative action...

September 26, 2013, 20:33
#3
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Quote:
 Originally Posted by mouli1991 Im very bad in basics to understand here all fluids --> Bernoulli's equation we got P+1/2 v^2/2+rho*g*h Here instead of p can we insert Internal energy U as we do in First law of thermodynamics. If yes, then can we say that Internal energy can also be any energy acting inside a system (Microscopic and macroscopic). If no why is that?
It is enthalpy, not internal energy: Google Bernoulli equation for compressible flows or look corresponding section at

http://en.wikipedia.org/wiki/Bernoulli%27s_principle

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