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I m having a little problem with the definition of work:

-Mechanical work is a force applied through a distance, defined mathematically as the line integral of a scalar product of force and displacement vectors. Work is a scalar quantity which can be positive or negative.

-In thermodynamics, thermodynamic work is the quantity of energy transferred from one system to another. It is a generalization of the concept of mechanical work in mechanics.

----->now my real problem comes when i take free gas expansion as an example:normaly work should be equal to 0 (thats what i read in books)

How can that be since we have an expansion DV and obviously a force responsible for that expansion P (pressure).

In my book it says that work in tha case of free expansion equals to 0 because it defines work as:

-distance * force resisting to the movement.

In that case i agree that free gas expansion work equals 0 since there is nothing resisting the expansion, however that third definition is in contradiction with the first one.

I am so confused.Please help!!

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# Problem with the definition of work

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