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Thermodynamics and waves problems

  1. Apr 15, 2016 #1
    1. The problem statement, all variables and given/known data
    1.
    A gas expands as shown in the graph. If the heat taken in during this process is 1.02 × 10^6 J, the change in internal energy of the gas (in J) is
    2.
    One mole of an ideal gas is held at a constant pressure of 1 atm. Find the change in volume if the temperature changes by 50°C.
    3.
    Two harmonic waves traveling in opposite directions interfere to produce a standing wave described by y = 2 sin (π x) cos (3π t) where x is in m and t is in s. What is the distance (in m) between two adjacent antinodes?

    2. Relevant equations
    pV=nRT
    W= -p(V2-V1)
    E= Q+W
    3. The attempt at a solution
    1.
    E=Q+W
    E=1.02*10^6+[-p(V2-V1)]
    E=1.02*10^6-(6-2)(8-2)
    It seems incorrect

    2.
    pV=nRT
    1*V=1*8.31*(50)
    V=416 m^3
    3.
    k=2pi/λ
    pi=2pi/λ
    λ=2
    pi=[3pi]/λ
    λ=3
    the distance is 3-2=1
     

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  3. Apr 15, 2016 #2

    rude man

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    Incorrect. p is not constant with V.
    Right. Get the right W.
     
  4. Apr 15, 2016 #3

    SteamKing

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    Staff Emeritus
    Science Advisor
    Homework Helper

    When you have three different HW problems, the recommended procedure is to start a thread for each problem. It is less confusing that way.
     
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