Negative Work
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Negative Work
Hi! I was doing the Sapling homework for Week 3/4 and question 17 involved a negative value for work. Can someone please explain why work done by the system is a negative value? Thanks!
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Re: Negative Work
The problem states that work is done by a system, which means it is a negative value. I think we just have to remember that work done by a system is negative and work being done on a system is positive. The way I rationalize this is by saying that when the system is doing work, it is losing energy to do this work, which makes the value negative.
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Re: Negative Work
When work is done to the system, the value is positive. When a system does work, the value is negative.
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Re: Negative Work
The best way to sum it us is to remember that when work is done to the system you get a positive value and when a system does work you get a negative value. I think this is the opposite for physics because there you are looking at what is happening to the universe verses chem where we are looking at the relationship in terms of the system.
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Re: Negative Work
When a system does work, there is a negative value for work because you can think of it as energy being inputted (and thereby released) by the system. The surroundings of the system would then absorb that energy inputted. However, when work is done to a system, the system itself is essentially absorbing that energy, thereby making work positive.
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Re: Negative Work
When work is being done to a system, the work will be positive and if work is being done by the system, the work will be negative.
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Re: Negative Work
Work done by the system is negative because the system is expending energy to complete a task which for our class will be expanding the volume of a container. Whereas, work being done on the system will most likely be in reference to the system or container being compressed which is a way of transferring energy from the surroundings into the system.
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Re: Negative Work
The work done by a system is going to be negative because it is releasing/losing energy to its surroundings
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Re: Negative Work
Hey! So like others said, when a system does work on its surroundings, the work will be negative. This is why in our expansion example problems in class, they were all negative work. Expansion means the system is pushing the piston outwards, and thus doing work on its surroundings. Compression would be positive work, because the surroundings are doing work ON the system.
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Re: Negative Work
When work is done on the system, the system gives off energy to the surroundings instead of expending energy to do work, thus work is negative.
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Re: Negative Work
The reason why its negative is because we are not thinking about it in terms of physics where we think of work as leaving/entering the surroundings, we are concerned about the system.
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Re: Negative Work
If work is done on the system, w is a positive value. If the system does work, then w is a negative value. Hope that helps :)
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Re: Negative Work
Work done by the system is a negative value because we are looking generally at the working being done TO the system. If the system does the work, it means that its losing it to its surroundings thus why the work of the surroundings would be positive and the system would be negative.
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Re: Negative Work
This is because when a system is expanding/voluume is increase, it is doing work of expansion so its losing energy, explaining why the sign for work would be negative
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Re: Negative Work
Because the function for work is looking at work done from the perspective of the system. To the system, it is losing its ability to do work, by doing work.
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Re: Negative Work
Hi! When work is done by the system, the value is negative because it is losing/releasing energy into the surroundings through doing work. When work is done on the system, the value is positive because the system gains energy from its surroundings. Hope this helps! :)
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Re: Negative Work
If the work is negative than that means the system is doing work. When it does work it loses or uses energy hence the reason its negative.
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Re: Negative Work
If work is negative then that means that the system is doing work on its surroundings, so it is losing energy.
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Re: Negative Work
Hi! If the system is doing work on the surroundings, then the work would be a negative value.
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Re: Negative Work
I believe that when work is done on the system, the work value is positive. But when the system does work then the value is negative.
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Re: Negative Work
When the system is expanding/doing work, it is pushing eternal air out of the way in order to expand, therefore doing work. And when the system does work it is losing energy, making the work term a negative value
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Re: Negative Work
If a system is doing work, its internal energy should decrease (I like to think of myself as the system; if I exercise, I have less energy). Thus, work must be negative in order to lower the value of U.
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Re: Negative Work
Work done by the system is a negative value because it will cause the internal energy of the system to decrease. Quantitatively speaking, U = q + w, and if the work being done by the system is less than zero, then it will cause a decrease in internal energy. I hope this helped!
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Re: Negative Work
I believe that work done by the system is negative because it releases energy from the system. By the same idea, work done on the system is positive because energy is being put into the system. It can be confusing since, at least for me, there was never a good explanation given by the teacher/professor whenever I learned/relearned about work.
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Re: Negative Work
When work is negative the system performs the work. When work is positive the work is done to the system.
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Re: Negative Work
Hello, so when work is done by the system, the final value would be negative. This is because the system is losing energy into the surroundings by doing work. When work is done on the system, the resulting value would end up being positive because the system gains energy from its surroundings. For some reason, it took me a while to understand this but hope this kinda helps.
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Re: Negative Work
As others have said, work being done by the system is negative. A helpful way to remember this is to visualize the system giving away work! Since its giving away work by doing work, work is negative for the system.
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