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Kyle Rex 1K
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Joined: Sat Aug 17, 2019 12:16 am


Postby Kyle Rex 1K » Wed Jan 29, 2020 10:56 pm

if work is a piston compressing the gas and the work is given as 300kJ (for example), when solving for delta U of the gas inside a close container using delta U=q+w, would w be positive or negative?

Alicia Lin 2F
Posts: 83
Joined: Wed Sep 18, 2019 12:17 am

Re: 4B.1

Postby Alicia Lin 2F » Wed Jan 29, 2020 11:12 pm

It is positive because the force exerted is in the same direction as the displacement. And when work is done on the system, it is positive.

Gurmukhi Bevli 4G
Posts: 49
Joined: Wed Nov 14, 2018 12:20 am

Re: 4B.1

Postby Gurmukhi Bevli 4G » Thu Jan 30, 2020 12:29 am

It would be positive since work is being performed on the system.

Leonardo Le Merle 1D
Posts: 56
Joined: Wed Feb 27, 2019 12:16 am

Re: 4B.1

Postby Leonardo Le Merle 1D » Thu Jan 30, 2020 10:08 am

Think about the energy of the gas; because a force is being exerted on it (W), that results in an increased pressure and energy (U) in that system - it might heat up as a result.

Bryce Barbee
Posts: 103
Joined: Wed Sep 18, 2019 12:20 am

Re: 4B.1

Postby Bryce Barbee » Thu Jan 30, 2020 10:42 am

In that equation, the Work is equal to Work(on the system). Therefore work would be positive because the system is being compressed by the piston.

Abby Soriano 1J
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Joined: Sat Aug 24, 2019 12:16 am

Re: 4B.1

Postby Abby Soriano 1J » Thu Jan 30, 2020 11:19 am

It's always a good idea to think of both work and heat from the perspective of the system. We know that endothermic reactions are categorized with a +delta H since they are taking in heat. With that same concept, we can think of positive work or heat as being applied to the system. If heat is added to the system q is positive. If work is being done to the system, w is positive.

Betania Hernandez 2E
Posts: 107
Joined: Fri Aug 02, 2019 12:15 am

Re: 4B.1

Postby Betania Hernandez 2E » Thu Jan 30, 2020 10:12 pm

It would be positive since work is being done on the system.

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