## HW problem 4A.3 from 7th edition

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Emily Huang 1E
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

### HW problem 4A.3 from 7th edition

I am confused as to why delta V=pi*r^2*d according to the solution manual. Where did the book get that equation from and do we need to know that equation?

Erin Kim 2G
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

### Re: HW problem 4A.3 from 7th edition

That is just the standard volume equation for a cylinder, and since volume is not constant for this piston we would use this equation to find out the change in volume for the pump. This is a standard math equation that should be known I believe, it is not on the constants and equations sheet.