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Thread: Thermodynamics question

  1. #1 Thermodynamics question 
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    This is a past exam question, not a homework question. I don't have the solutions, so I wanted to check if I had it right.

    "An isolated cylinder contains one litre of monatomic ideal gas at 300K and pressure of 10^5 N/m^2. At one end there is a massless piston with surface area 0.01m^2. The cylinder is compressed very fast (non-quasistatically) by the piston exerting an external force of 10000N. The piston moves by 1 millimetre."

    So that is the set up. I'm interested in the work done (on the system), and heat added.

    So if is work done on the system, then is this right?

    ;

    ;

    So ?

    I'm having a bit of a mental block when it comes to the heat added, though. If anyone could help me with that?

    After I get that i need change in internal energy and change in entropy, so that would just be and yes?

    Thanks in advance


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  3. #2 Re: Thermodynamics question 
    sox
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    Quote Originally Posted by em12
    This is a past exam question, not a homework question. I don't have the solutions, so I wanted to check if I had it right.

    "An isolated cylinder contains one litre of monatomic ideal gas at 300K and pressure of 10^5 N/m^2. At one end there is a massless piston with surface area 0.01m^2. The cylinder is compressed very fast (non-quasistatically) by the piston exerting an external force of 10000N. The piston moves by 1 millimetre."

    So that is the set up. I'm interested in the work done (on the system), and heat added.

    So if is work done on the system, then is this right?

    ;

    ;

    So ?

    I'm having a bit of a mental block when it comes to the heat added, though. If anyone could help me with that?

    After I get that i need change in internal energy and change in entropy, so that would just be and yes?

    Thanks in advance
    Forgive me if I'm wrong here, I'm quite tired. Perhaps you should consider it like this though.

    Work done = Force x Distance

    Where the force is the force that the piston exerts, and the distance is the distance that the piston moves.

    This work is done on the gas. That is, it is energy put into the gas. So this is the added heat.

    Again apologies if I've misread or forgotten something basic. I'm mentally fatigued at the minute - exams and all that jazz.



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