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Homework Help: Thermal expansion: Plastic Molding

  1. Feb 14, 2012 #1
    1. The problem statement, all variables and given/known data
    ABS plastic melts (and solidifies) at 105 °C. You want to inject it into a steel mold. When the part comes out at 20°C you want it to be 7.250cm long. Edit: If this isn't clear, it wants to know how big the steel mold should be.
    α for ABS plastic α= 53.0x106/C°, for steel α= 11.0x106

    2. Relevant equations

    3. The attempt at a solution
    Ok so I used the equation for linear expansion and I come out with an initial length of 7.282cm. The answer I'm given is 7.276cm. I'm think this has something to do with the steel but I have no idea what.
    Edit: I tried a similar problem and got the right answer using the same method. I have no idea.
    Last edited: Feb 14, 2012
  2. jcsd
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