# (easy) Isobaric processes mastering question

Foremost, this is my first post on PF, but I have used the sites archives extensively for help on my physics homework this semester, so many thanks to all! You have no idea how much you helped save me time, points, and also improved my understanding of the material.

But I'm stuck on a very simple question related to isobaric (constant pressure) processes for ideal gases.

1) Statement of the Problem:

"A gas undergoes the process shown in the figure. By what factor does the temperature change? "

http://session.masteringphysics.com/problemAsset/1070958/3/16.Q10.jpg

"T(f)/T(i) = ?"

2) Relevant equations:
V(i)/T(i) = V(f)/T(f) (Charle's Law, for isobaric processes)
pv = nRT

3) Attempt at solution:

This should be very simple: T(f)/T(i) = V(f)/V(i), assuming moles stay the same. I just applied the ideal gas law, eliminated the constants (p, n, R).

At constant pressure: V(f)/T(f) = V(i)/T(i), then I solved for the V-terms to get:
T(f)/T(i) = V(f)/V(i)

But mastering physics says "answer does not depend on variable V(f) or V(i)" and evaluates those variables to random number values.

Did I do something wrong, or is this a formatting problem with mastering? Its gotta be something very simple, so I will update with a solution if my prof gets back to me.

Thanks for any help!

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collinsmark
Homework Helper
Gold Member
Hello bikeman86,

Welcome to Physics Forums!

By examining the figure, you'll notice that the figure is labeled with 0 at the origin, and has tick marks on the x-axis. Based on this, ask yourself, "By what factor does the volume change?"

Oh my gosh, that was needlessly painful. For the final time this semester, thank you Mastering for making something so simple so unnecessarily ambiguous. Three "tick" marks over one "tick" mark = answer = completely ambiguous waste of time and energy.

Nonetheless, thanks for your help collinsmark!