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## Main Question or Discussion Point

Some examples in text book make me confused when these two works are discussed at the same time.

One of the works is the (mechanical) work in work-energy theorem:

[tex]

\Delta K = \sum_iW_i,

[/tex]

where [tex]K[/tex] is the kinetic energy and [tex]W_i[/tex] was the work done by the [tex]i[/tex]-th force.

The other is the (thermodynamical) work in the first law of thermodynamics:

[tex]

\Delta U = Q + W,

[/tex]

where [tex]U[/tex] is the internal energy of the system, [tex]Q[/tex] is the heat transfered, and [tex]W[/tex] is the work done on the system by surroundings.

Are the two works the same when we want to use work-energy theorem and the first law of thermodynamics at the same time?

Can any one give some criterion to distinguish these two works ?

Thank you .

One of the works is the (mechanical) work in work-energy theorem:

[tex]

\Delta K = \sum_iW_i,

[/tex]

where [tex]K[/tex] is the kinetic energy and [tex]W_i[/tex] was the work done by the [tex]i[/tex]-th force.

The other is the (thermodynamical) work in the first law of thermodynamics:

[tex]

\Delta U = Q + W,

[/tex]

where [tex]U[/tex] is the internal energy of the system, [tex]Q[/tex] is the heat transfered, and [tex]W[/tex] is the work done on the system by surroundings.

Are the two works the same when we want to use work-energy theorem and the first law of thermodynamics at the same time?

Can any one give some criterion to distinguish these two works ?

Thank you .