Q 8.13


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Belle Calforda3f
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Joined: Fri Sep 29, 2017 6:07 am

Q 8.13

Postby Belle Calforda3f » Mon Jan 15, 2018 9:14 pm

In question 8.13, why is 947 kj absorbed written as a negative q value?

Cali Rauk1D
Posts: 51
Joined: Fri Sep 29, 2017 6:03 am

Re: Q 8.13

Postby Cali Rauk1D » Mon Jan 15, 2018 9:21 pm

It is negative because heat is being absorbed from the system

Keliana Hui 2E
Posts: 82
Joined: Fri Sep 29, 2017 6:07 am

Re: Q 8.13

Postby Keliana Hui 2E » Mon Jan 15, 2018 9:34 pm

947 kJ of energy is leaving the system as heat to the surrounding

Ammarah 2H
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Joined: Fri Sep 29, 2017 6:06 am

Re: Q 8.13

Postby Ammarah 2H » Tue Jan 16, 2018 10:23 am

So just for clarification, if heat is absorbed by the system, is the value always negative?

Kelly Kiremidjian 1C
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Joined: Fri Sep 29, 2017 6:04 am

Re: Q 8.13

Postby Kelly Kiremidjian 1C » Tue Jan 16, 2018 11:36 am

No. In this question, it says that the cooling system that surrounds the cylinder absorbs 974 kJ of heat. If the system that surrounds the cylinder is absorbing heat, this means that the cylinder is releasing this heat and that is why it is negative.
Heat absorbed by the cylinder would be positive, heat leaving the cylinder is negative.

905022356
Posts: 48
Joined: Mon Oct 02, 2017 6:19 am

Re: Q 8.13

Postby 905022356 » Wed Jan 17, 2018 5:24 pm

I don't understand why the final answer is negative. Can someone explain it to me? thanks!

Jennie Fox 1D
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Joined: Sat Jul 22, 2017 2:01 am

Re: Q 8.13

Postby Jennie Fox 1D » Wed Jan 17, 2018 5:37 pm

If the system is doing work on its surroundings, as in this problem, the work is negative.

Magdalena Palavecino 1A
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Joined: Fri Sep 29, 2017 6:04 am

Re: Q 8.13

Postby Magdalena Palavecino 1A » Wed Jan 17, 2018 11:00 pm

Does it matter if we are talking about work or heat? I understand that when heat is lost it is negative, but what about work? I am confused about these two terms

Sally Nason - 1K
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Joined: Fri Sep 29, 2017 6:05 am

Re: Q 8.13

Postby Sally Nason - 1K » Thu Jan 18, 2018 11:40 am

In this question, the part we are trying to figure out is the work that can be done by the system, or on the system. In general, if the system does work, such as expansion, the work value will be positive and if the system has work done on it, such as compression, the work value will be negative.

Amy Zheng 2l
Posts: 57
Joined: Fri Sep 29, 2017 6:04 am

Re: Q 8.13

Postby Amy Zheng 2l » Thu Jan 18, 2018 10:21 pm

the system is doing work on the surrounding so its negative


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