1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Galaxy Rotation Curve problem -

  1. Jan 31, 2010 #1
    Hi folks,

    I'm supposed to derive the func. form of the rotation curve for the outer parts of our galaxy, in the absence of dark matter.

    Im assuming that I treat this as a linear curve, since in reality, dark matter flattens out the curve, when it should continue following the linear(?)

    What I've done:

    1) v= rw v = Vel, r = distance from centre w = angular freq. (d(theta)/dt)
    2) v²/r = GM(r)/r²

    What do I do now? If I subs. 1 into 2, I get stuck with w and M(r).

    How am I supposed to treat M(r): (M(r) = [(4/3)*Pi*r³]*p)
    Do I just introduce p (density) into the eqn. and assume p is constant?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted