## Q5 on the midterm

$\Delta U=q+w$

Mary Becerra 2D
Posts: 53
Joined: Fri Sep 29, 2017 7:06 am

### Q5 on the midterm

In step 1 we find that the work done by the system is -158J. How can we make the conclusion that in step 2, our U = +158J? I thought that since there is no heat exchange, w=U.

Jonathan Tangonan 1E
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

### Re: Q5 on the midterm

The delta U is +158J because in step 2 it returns to its original internal energy. So, the work the system had done which was -158J returns back to its original state by saying delta U of the second step is +158J.