Signs on energy changes

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Michelle Steinberg2J
Posts: 73
Joined: Fri Sep 29, 2017 7:04 am

Signs on energy changes

Postby Michelle Steinberg2J » Mon Jan 15, 2018 5:01 pm

I am having difficulty with determining the correct signs on energy changes. For example, HW problem 5, why is compression a positive value? Also, HW problem 7 says the system "absorbed 492 J of heat." Why is this a negative value?

Thanks!

Hammad Khan 2B
Posts: 51
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

Re: Signs on energy changes

Postby Hammad Khan 2B » Mon Jan 15, 2018 6:53 pm

In problem 5,the compression is a positive value because work is being DONE TO the system meaning that energy is being added to it in the form of work. In problem 7, when it says "absorbed heat" it's saying how heat is essentially being taken into a system as it's increasing in energy. The equation is usually written as but it is rearranged into to solve for work. So it is not exactly "negative".

804899546
Posts: 51
Joined: Sat Jul 22, 2017 3:00 am

Re: Signs on energy changes

Postby 804899546 » Mon Jan 15, 2018 7:55 pm

So in number 7, would it be endothermic because it is absorbing heat?

Jessica Jones 2B
Posts: 80
Joined: Fri Sep 29, 2017 7:04 am

Re: Signs on energy changes

Postby Jessica Jones 2B » Mon Jan 15, 2018 8:40 pm

yes it would be endothermic!


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