- #1

- 149

- 0

## Main Question or Discussion Point

Hi folks,

in this book (correct page should open, if not: p.199): http://books.google.com/books?id=12...r thermodynamics&pg=PA199#v=onepage&q&f=false

it says (formula (7.168)):

[tex]<\sum_i \vec{r}_i \vec{F}_i > = -p \oint{\vec{r} d\vec{S}}[/tex]

It is explained, why dF=-p dS, but I dont see the connection between the mean value of the sum on the left hand side and the ring integral on the right hand side.

Best,

derivator

in this book (correct page should open, if not: p.199): http://books.google.com/books?id=12...r thermodynamics&pg=PA199#v=onepage&q&f=false

it says (formula (7.168)):

[tex]<\sum_i \vec{r}_i \vec{F}_i > = -p \oint{\vec{r} d\vec{S}}[/tex]

It is explained, why dF=-p dS, but I dont see the connection between the mean value of the sum on the left hand side and the ring integral on the right hand side.

Best,

derivator