umdnjmed

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The net work done ON a certain gas is 55J, the net heat flow into the gas is -23J. What is the net work done BY the gas?
A. -55J
B. 0J
C.32J
D.78J

Since the NET WORK done ON the gas is 55J, shouldn't the answer to the question be B?
 

milski

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Work done ON something is the opposite of work done BY something. It's similar to a take/give relationship - if you took 5 apples, you gave (-5) apples.

B would imply that no work was done at all.
 

umdnjmed

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Work done ON something is the opposite of work done BY something. It's similar to a take/give relationship - if you took 5 apples, you gave (-5) apples.

B would imply that no work was done at all.

I may be missing a really basic concept; I think my confusion stems from the use of the phrase "NET WORK." If a net work of 55J is done on the system, doesn't this mean the work done BY the system has already been taken into consideration. if 55J of work is done on the system and 55J of work is done by the system, wouldn't the net work be zero, not 55?
 

milski

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I may be missing a really basic concept; I think my confusion stems from the use of the phrase "NET WORK." If a net work of 55J is done on the system, doesn't this mean the work done BY the system has already been taken into consideration. if 55J of work is done on the system and 55J of work is done by the system, wouldn't the net work be zero, not 55?

Yes, it's mostly a terminology confusion. You cannot talk about "WORK" in general - it always has to be work ON something. It's either "work done on something by something" or it's "net work on/by something". The latter is the total of all the former.

In this case they are talking about net work on/by the gas.
 
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