1. Not finding help here? Sign up for a free 30min 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!

Lagrange constraint mechanics problem

  1. Oct 25, 2010 #1
    http://img221.imageshack.us/img221/3754/capturetp.png [Broken]

    Just a simple question. I can see that for this to work I need:

    Trot = 1/5 ma2(thetaDOT + phiDOT)2

    Just can't work out what phi has to do with rotational kinetic energy. I would have thought it would need to be simply the same thing but without the phiDOT term.
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 25, 2010 #2


    User Avatar
    Homework Helper

    [itex]\theta[/itex] is the angular position of an identified point on the smaller sphere, measured with respect to the line joining the centers of the two spheres, right? Note that not only does [itex]\theta[/itex] change with time, but so does the orientation of that joining line, so you need to take that into account as well. That's where the [tex]\dot\phi[/tex] comes from.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Lagrange constraint mechanics problem
  1. LaGrange problem (Replies: 1)

  2. Lagrange mechanics (Replies: 8)