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Positive or negative work

Posted: Wed Feb 12, 2020 12:43 am
by Petrina Kan 2I
Is work positive when work is done on the system? I am finding varying answers online which is making me confused.

Re: Positive or negative work

Posted: Wed Feb 12, 2020 1:17 am
by Morgan Carrington 2H
The answer can vary depending on which perspective you are looking at, but when focusing on the system work is positive when work is done on it.

Re: Positive or negative work

Posted: Wed Feb 12, 2020 1:27 am
by Long Luong 2H
I like to think of a bicycle pump. When you push the pump down, you are exerting a positive force in work on the pump. However, if the gas were to push back against you, it is counteracting your work, so it’s negative work done by the pump (system).

Re: Positive or negative work

Posted: Thu Feb 13, 2020 1:27 am
by Gurmukhi Bevli 4G
It depends but generally it would be positive when work is being done on the system and negative when the system is performing work on the surroundings

Re: Positive or negative work

Posted: Thu Feb 13, 2020 2:34 am
by Justin Seok 2A
When work is done on the system, it is positive, and when the system does work on its surroundings, it is negative.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 8:47 am
by Connor Chappell 2B
When work is done on the system, work is positive. This is due to the fact that the reaction's capacity to do work has INCREASED. The same can be said for a reaction where work is done on the surroundings and the sign is negative because the reaction has lost energy to its surroundings in the form of work.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 8:51 am
by 805373590
When work is done on the system it is positive and when work is done by the system it is negative

Re: Positive or negative work

Posted: Thu Feb 13, 2020 8:56 am
by aphung1E
I am confused as well especially when utilizing the equation W=-nRT sometimes the solution is positive work instead of negative. How can I tell if it’s negative or positive even if the equation has a negative sign in it?

Re: Positive or negative work

Posted: Thu Feb 13, 2020 10:52 am
by Max Madrzyk Dis 4G
if you have a system that work is done on then the work of the system will be positive, if you have a system and work is done by it then work of the system will be negative. I think of it as the system is using energy to do some work on the outside so it is losing that energy.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 12:59 pm
by Robin Cadd 1D
If the system does the work, the work is negative.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 4:31 pm
by Eunice Nguyen 4I
Work is negative if the system does work on surroundings, while being positive if the surroundings do work on the system.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 4:34 pm
by Anna Heckler 2C
Determining the sign of work is based on what you decide is your system and what is your surroundings - it's relative. Positive work means that work was done on the system, so it gains energy. Negative work means that work was done by the system, and the system loses energy.

Re: Positive or negative work

Posted: Thu Feb 13, 2020 4:36 pm
by 504939134
If you have work being done on the system then work will be positive, and if work is being done by the system then work will be a negative value.

Re: Positive or negative work

Posted: Sat Feb 15, 2020 11:48 am
by Matthew Tsai 2H
Generally we refer to everything from the perspective of the system, which means that positive work means that work is being done on the system. You can also think of doing work ON some system as adding energy to it, so it makes sense that work is positive.

Re: Positive or negative work

Posted: Thu Mar 12, 2020 10:29 pm
by ramiro_romero
When work is done on the system, it is positive. When work is done by the system onto surroundings, it is negative. If the system exerts force on its surroundings, the system itself loses energy, explaining the negative value.

Re: Positive or negative work

Posted: Fri Mar 13, 2020 6:08 pm
by Joowon Seo 3A
work is positive when it is done on the system. When the system does work, the work is negative.