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Piston Compressing a Spring

  1. Jan 31, 2007 #1
    1. The problem statement, all variables and given/known data
    A horizontal piston is attached to a spring with a spring constant of 1500N/m. The cross sectional area of the cylinder is A=10cm^2, it contains 0.0040mol of gas. At 20 deg Celsius the spring is neither compresssed nor stretched. How far is the spring compressed, x, if the gas temperature is raised to 100 deg Celcius?

    2. Relevant equations
    PV=nRT ...(P_1 * V_1)/T_1 = (P_2 * V_2)/T_2

    3. The attempt at a solution
    I assume that the increased volume V_2 = V_1 + Ax. And P_1 is standard pressure, and i need to work in Kelvins, but I have tried everything I know to get the right answer but can not.
    I know the answer via the back of our textbook which is 1.02cm. But it is a problem we need to show our work on, and I can't figure this one out. Any help would be greatly appreciated.
  2. jcsd
  3. Jan 31, 2007 #2


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    Homework Helper

    What's the definition of pressure? What would the force applied on the spring be equal to (Hint: Consider Hooke's Law) ?
  4. Feb 1, 2007 #3
    Also be very careful re units--this came up recently in a similar problem, where atmospheres of pressure need to converted to Bars, and volume units made to be the same, eg 1 liter is a 1000cm^3.
  5. Feb 1, 2007 #4
    yeah, Pressure = F/A, and F = -kx => -kx/A must equal the pressure exerted by the spring. I have all my units in Pa, m^3, and K, i really dont know where I am going wrong,
  6. Feb 1, 2007 #5
    last time this came up, the soln was a quadratic, maybe if you posted the completed eqn with all the subs and algebra, we may me able to comment
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