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Find length of spring A in equilibrium position

  1. Sep 23, 2015 #1
    As shown in Figure Q1a, a frictionless, massless, piston, supported by two springs, A and B, is held by a pin in a vacuum inside a rigid-walled container. The properties of the springs are: spring constants kA = 3,859 and kB = 3,090 (in N/m), natural lengths LA0 = 0.03 and LB0 = 0.1 (in m). When the piston is pinned to the wall, the lengths of the springs are LA1 = 0.1 and LB1 = 0.1 (in m), respectively. Both springs possess dissipative properties so that after the pin is pulled, the piston eventually comes to rest at an equilibrium position. Find the length of spring A in this equilibrium position (LA2) in units of m.

    Equations so far:
    Elastic Energy Constituitive Relation: (E2 - E1) = (k/2)(x22 - x12)

    First Law of thermodynamics: (E2 - E1) = (Q1-2) - (W1-2)
    Second Law of thermodynamics...

    Don't really know where to start? Help appreciated
  2. jcsd
  3. Sep 23, 2015 #2


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    Hello Ally, welcome to PF :smile: !

    You bring in thermodynamics, but is that really intended for this exercise ? I don't see any other given than "vacuum" , so I must assume that applies to both volume A and volume B. And then the exercise becomes a simple force balance.
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