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# Re: [Phys-l] PV question

• From: Leigh Palmer <palmer@sfu.ca>
• Date: Sun, 24 Jan 2010 21:27:34 -0800

It appears my ASCII art abilities don't quite measure up. Going through the listserv I lost WYSIWYG fidelity. This is an experiment; I'll try to correct my errors and improve on the original:

On 24 Jan 2010 what I wrote came through the listserv (as digest) like this:

1. The work done by the gas is the integral of PdV over the process (B to A, or 2Vo to Vo). In this hypothetical process that would be carried out over that portion of the curve

[ V ]
P = Po [ 3 - - ]
[ Vo ]

The answer is That the work done by the gas is - 3/2 PoVo.

I am sure everyone will agree on that.

I want to point out that the ASCII art above is drawn misleadingly from a pedagogical point of view. It would not have been much more difficult to draw it without a suppressed zero on the pressure axis. Then the answer can be read off the graph as an area:

2Po+ |\A
| | \
| | \
| | \
Po+ | \B
| | |
| | |
| | |
+---+----+-
Vo 2Vo

1. The work done by the gas is the integral of PdV over the process (B to A, or 2Vo to Vo). In this hypothetical process that would be carried out over that portion of the curve

/ V \
P = Po | 3 - --- |
\ Vo /

The answer is That the work done by the gas is - 3/2 PoVo.

I am sure everyone will agree on that.

I want to point out that the ASCII art above is drawn misleadingly from a pedagogical point of view. It would not have been much more difficult to draw it without a suppressed zero on the pressure axis. Then the answer can be read off the graph as an area:

2Po+ |\ A
| | \
| | \
| | \
Po+ | \ B
| | |
| | |
| | |
+----+----+-
0 Vo 2Vo

etc.

Let's see how that translates. If it doesn't work, perhaps someone would let me know what I'm doing wrong.

Thanks,

Leigh