Manipulating derivatives and rearranging

[cooev769]

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.

 

[jbunniii]

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.

 

[micromass]

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.

https://www.physicsforums.com/showpost.php?p=3977517&postcount=3

 

[jbunniii]

https://www.physicsforums.com/showpost.php?p=3977517&postcount=3

I linked it in my post too (see blue FAQ link) but now that I look at it, it doesn't show up very well.

 

[micromass]

I linked it in my post too (see blue FAQ link) but now that I look at it, it doesn't show up very well.

I totally missed that... Perhaps I'm going blind

 

[cooev769]

Cheers. Turns out the equations they gave us to derive was incorrect. So thread closed.