## Work

$\Delta U=q+w$

Nathan Mariano 2G
Posts: 68
Joined: Fri Sep 28, 2018 12:29 am

### Work

How can we determine whether the work is performed by or on the system? What makes work positive or negative in terms of the system?

armintaheri
Posts: 68
Joined: Fri Sep 28, 2018 12:26 am

### Re: Work

Work is positive (done on the system) if it adds energy to the system. For example, if you increase the pressure of a gas using a piston, you are doing work on the gas because you are adding energy to it. If you heat a gas, you are adding energy to it, therefore you are doing work on it.

Phil Timoteo 1K
Posts: 101
Joined: Fri Apr 06, 2018 11:05 am

### Re: Work

So does that mean work can't be negative?

ryanhon2H
Posts: 60
Joined: Fri Sep 28, 2018 12:28 am

### Re: Work

Work can be negative if it is done by the system, opposite of doing work on the system in that heat is released in contrast to adding heat, or energy.

JT Wechsler 2B
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

### Re: Work

If work is done on the system it is positive. If work is done by the system it is negative. This is kind of like temperature changes in a system being endothermic and exothermic. If heat is being given into a system it’s positive and if heat is leaving the system it’s negative.

AlyssaBei_1F
Posts: 99
Joined: Fri Sep 28, 2018 12:17 am

### Re: Work

I think of work like exothermic and endothermic. Doing work on a system is positive because you are adding energy. Work by a system is negative because energy is released.

Kaylee Kang 1G
Posts: 65
Joined: Fri Sep 28, 2018 12:24 am

### Re: Work

If work is positive, then it is adds energy into the system. If it is negative, energy is released!