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Homework Help: Piston problem ( closed system )

  1. Jan 29, 2012 #1
    1. The problem statement, all variables and given/known data

    1. A piston cylinder arrangement ( A = 0.25 m^2, P1= 200 KPa, V1= 0.05 m^3. is loaded with a linear spring. in the current configuration the spring exerts no force on the piston head. if the atmospheric pressure is 101 KPa, what is the mass of the piston head. Heat is now added casing the bolume to double, what is the new pressure? how many air Blobs( mean this closed system) do we encounter in this transformation?

    I calculated and my answer is mass =2520 Kg .
    P2= 240KPa
    the third part (how many air Blobs( we named the closed system as blob) do we encounter in this transformation?) i don't understand it at all i need help in it ...
    this is the 2nd question i don't understand it at all what i have to do and what's the x axis and y axis

    2. assume that our transformation in problem 1 is reversible. in the (V,p) plane, plot the transformation between the initial and final states ( hint: solve our force balance equation for p, tnow substitute for y= V/A if you have not already done so this will give pressure as a function of volume: p=p(V) where all other parameters are constant. Plot p(V) !)

    please please help XD
  2. jcsd
  3. Feb 1, 2012 #2

    rude man

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    Homework Helper
    Gold Member

    I thought I had posted on this before.

    I said then, and I repeat now, that the spring constant (k = Δp/ΔV) must be known to determine p2.

    Once k is known, all parameters can be computed, including T2, p2, ΔU, W and Q, ideal gas assumed.

    The mass is correctly computed (actually 2523 kg).

    The only blob I know of is the one in the 1958 indie movie with Steve McQueen ....
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