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Homework Help: A Thermodynamics Problem

  1. Apr 27, 2007 #1
    1. The problem statement, all variables and given/known data

    Two 800 cm^3 containers hold identical amounts of a monatomic gas at 20 degrees C.
    Container A is rigid.
    Container B has a 100 cm^2 piston with a mass of 10 kg that can slide up and down vertically without friction.

    Both containers are placed on identical heaters and heated for equal amounts of time.

    Will the final temperature of the gas in A be greater than, less than, or equal to the final temperature of the gas in B?

    2. Relevant equations
    I don't know if equations are necessary.

    3. The attempt at a solution
    My professor attempted to cover 4 thermodynamics chapters in about 100 minutes. To say the least, he didn't do such a good job.

    I'm gonna assume I can ignore the part with the flame, since it's being applied to both cylinders.

    I know if you do work on the air molecules you can also increase the temperature.

    Question is though, since the piston moves up and down, does that imply its change in distance is 0 and in which case does it mean the amount of work it does = 0? Which further means its not increasing the temperature of the air molecules? Hence Temp (A) = Temp (B) ?
  2. jcsd
  3. Apr 27, 2007 #2


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    Gold Member

    HINT: The gas in B will gain energy from eating but then loose some energy because it will expand and raise the mass on the piston. If this is the case,will it gain less or more net energy than A? What now can you say about it temperature, relative to A?
  4. Apr 27, 2007 #3
    I'm not positive what you mean by "eating."

    But, I figure the gas in B will have to exert the same amount of energy it gained from the weight of the piston to raise it back up. In which case, I figure the temperatures are equal.
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