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Homework Help: Linearizing V=vw+(vo-vw)e^-kt

  1. Oct 11, 2012 #1
    Hi everyone!

    I have an issue with my physical chemistry lab. They ask us to rearrange the fallowing equation

    v=vw + (v0 - vw)e^-kt
    where v is velocity and t is time, vw is a constant

    They also ask which quantity would be plotted as ordinate and as absissa. We have to indicated the parameter of the slope and the intercept. Now once I have a equation I'll be able to find all those things but I can't seem to get to that equation.

    I was thinking of plotting it for velocity and time. We also need to be able to figure out k from the graph

    I tried for a while using the natural log of the function to lower the exponent and remove the e but I still cant seem to get a linear equation in which I'll be able to extract m and b.

    As you can see I'm a chemistry student, not very good with anything physics related, and sorry for the broken English, it's my second language :)

    Also sorry if this is in the wrong section, I'm new to this
  2. jcsd
  3. Oct 11, 2012 #2


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    Welcome to PF!

    Hi AlexLM! Welcome to PF! :smile:

    Try writing it as v - vw = (v0 - vw)e-kt :wink:

    (and btw, your English is fine :smile:)
  4. Oct 11, 2012 #3
    Hi tiny-tim! Thanks a lot for the answer!

    So basically if I graph for ln(v-vw)=ln(v0-vw) -kt I could use ln(v-vw) as my ordinate and t as my absissa. Then b would be ln(v0-vw) and the slope would be -k?

    Does that make sense?
  5. Oct 11, 2012 #4


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    yup! :smile:

    (oh, and it's "abscissa", from the Latin "abscindere" :wink:)
  6. Oct 11, 2012 #5
    If you do it on a semi-log plot, you don't actually have to calculate ln (v - v0). Your graphics package should have semi-log plot capabilities.
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