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Manipulating derivatives and rearranging

  1. Mar 24, 2014 #1
    Hey, I am actually a third year physics student, but here in New Zealand they tend to rush past the fundamentals, hence I can't seem to rearrange the following equations properly. Eq 1 and Eq 2 are:

    τ=-erB*dr/dt ek

    and

    τ=m*d(r^2dθ/dt)/dt ek

    Where ek is a unit vector. Is supposed to be rearranged to the form:

    vθ(r) = (-eB/mr) * integral between r and a of r dr = (-eB/mr)*(r^2-a^2)/2

    I can get very close but my derivative rearranging is sub-optimum. A little help would be really appreciated, as would telling me how the hell I write equations on the forum. Cheers.
     
  2. jcsd
  3. Mar 24, 2014 #2

    jbunniii

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    Regarding how to typeset equations on PF, there's a nice tutorial in section 2 of the FAQ, which should be more prominently visible but can be found under the "Site Info" link at the top of the page.
     
  4. Mar 24, 2014 #3

    micromass

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  5. Mar 24, 2014 #4

    jbunniii

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  6. Mar 24, 2014 #5

    micromass

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    I totally missed that... Perhaps I'm going blind :cry:
     
  7. Mar 24, 2014 #6
    Cheers. Turns out the equations they gave us to derive was incorrect. So thread closed.
     
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