Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Double pendulum velocity derivation

  1. Oct 2, 2010 #1
    I'm doing a personal project and I'm refreshing my knowledge on Lagrangian mechanics. Right now, I am looking at the double pendulum example. How is the velocity of the 2nd mass derived, in terms of the angles of the two rods? 2nd mass as in, the mass that hangs lowest.

    I have not been able to figure out the procedure to doing a derivation. The first mass velocity is relatively straightforward.
  2. jcsd
  3. Oct 2, 2010 #2
    I should probably give examples:

    I got [tex]v_1^2[/tex] rather easily:

    [tex]v_1^2 = l_1^2\dot\theta_1^2[/tex]

    But, v2 is expressed as:

    [tex]v_2^2 = l_1^2\dot\theta_1^2+l_2^2\dot\theta_2^2+2l_1l_2\dot\theta_1\dot\theta_2\cos{(\theta_1-\theta_2)}[/tex]

    I am getting the information from this page:

    Last edited: Oct 2, 2010
  4. Oct 2, 2010 #3
    I figured it out! Never mind!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook