Calculating Work Done in Baffling Thermodynamics Graph

AI Thread Summary
The discussion focuses on calculating the work done during a thermodynamic process represented by a pressure-volume graph. Participants clarify that work is determined by the area under the curve for each segment of the path, specifically using the formula work = P * delta-V. The graph's vertical divisions indicate pressure in pascals, while horizontal divisions represent volume in cubic meters, providing necessary scale for calculations. Participants emphasize understanding the changes in pressure and volume during transitions between points A, B, and C to compute work accurately. The conversation highlights the importance of grasping the relationship between area on the graph and the work done in thermodynamic processes.
jacksonpeeble
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Homework Statement


The pressure and volume of a gas are changed along the path ABCA in the graph. The vertical divisions on the graph represent 4.00 105 Pa, and the horizontal divisions represent 5.00 10-3 m3. Determine the work done (including algebraic sign) in each segment of the path.
cj6_p15-10alt.gif

(a) A to B = 0
(b) B to C
(c) C to A


Homework Equations


Area of Triangle=.5lwh
(0th and 1st Laws of Thermodynamics)


The Attempt at a Solution


What exactly am I supposed to figure out, and how am I supposed to go about doing this? I'm thrown off by the graph and what to do with it? What is it saying about the scale? If someone can explain HOW to get the numbers that I need to make the calculations (and why to use them), I can probably work it out (I assume I use the area of a triangle in there somewhere, but perhaps I'm wrong).
 
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Don't worry about the area... try rather to start by looking at each edge. That's what the question is asking.

For example... in going from A to B, what are the values for volume and pressure and how do they change? Can you figure out anything about the work done, just for this simple transition?
 
jacksonpeeble said:
What exactly am I supposed to figure out, and how am I supposed to go about doing this?

You're supposed to be figuring out the work done. Work is P*delta-V, so the work done from A to B, for example, is the area under the graph from A to B.

What is it saying about the scale?

There's no scale on the PV diagrams. The question's telling you what each grid represents.
 
...I hate to do it, but I'm going to have to ask for additional clarification. This just isn't clicking. :]
 
OK, one step at a time. Do you know why dW=P*dV? This is analogous to dx=v*dt, so it follows that because the area under a velocity-time graph is displacement, the area under a pressure-volume graph is work.
 
Ok :-)
 
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