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How far does the piston move

  • Thread starter bigboss
  • Start date
  • #1
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Homework Statement


The figure shows a 50 kg lead cylindrical piston that floats on 0.68 mol of compressed air at 30°C. How far does the piston move if the temperature is increased to 300°C? (the base of the beaker is 10cm.

A)130 cm B)1300 cm C)120 cm D)250 cm



Homework Equations




?

The Attempt at a Solution



no clue
 

Answers and Replies

  • #2
3,003
2


Think "Energy Balance"

Can you relate the internal energy change due to [itex]\Delta T[/itex] to the work needed to raise the piston?
 
  • #3
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is this a proper equation U= W+Q?
 
  • #4
3,003
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Yes. That is the "Energy Balance" for a thermodynamic system.

Now, what do each of the three terms represent?
 
  • #5
28
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internal energy= work + heat, and since temperature increases, internal energy increases also?
 
  • #6
3,003
2


Yes. Internal energy in a direct measure of the temperature change, you should have read somewhere that:

[itex]\Delta U=mc\Delta T[/itex] (or something similar depending whether it is a per mass basis or molecular basis) and that [itex]W=\int p\, dV[/itex]
 
  • #7
28
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ok so i have mass and change of T, how do i find C, also what do i do once i have change of U
 
  • #8
3,003
2


Generally, values of specific heat are tabulated in your text.

also what do i do once i have change of U
You tell me. What about your Work term? Your heat term Q is zero (I am assuming you can see why).

What is the work here? Can you find distance the piston travels using the Work term?

Hint: You were given area.
 

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