## GR0177 #37

mrodruck
Posts: 1
Joined: Sun Sep 23, 2012 11:09 pm

### GR0177 #37

The solution says that the overall work done is -300kJ. However, I can't figure out why it is negative. Shouldn't the work done by the isothermal process be positive, as W=PiVi*ln(Vi/Vf)? In this case, Vi > Vf which makes the ln function positive, and you know by looking at the graph it does more work than the isobaric process (which should be negative as W=-PdV). Therefore, I'd think it would have to be positive.

HappyQuark
Posts: 762
Joined: Thu Apr 16, 2009 2:08 am

### Re: GR0177 #37

mrodruck wrote:The solution says that the overall work done is -300kJ. However, I can't figure out why it is negative. Shouldn't the work done by the isothermal process be positive, as W=PiVi*ln(Vi/Vf)? In this case, Vi > Vf which makes the ln function positive, and you know by looking at the graph it does more work than the isobaric process (which should be negative as W=-PdV). Therefore, I'd think it would have to be positive.