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!

Classical Mechanics (Lagrangian)

  1. Oct 11, 2005 #1

    I'm looking for some advice on whether or not I'm doing a problem correctly.

    The problem is:
    A particle of mass m rests on a smooth plane. (the particle starts at r) The plane is raised to an inclination [tex]\theta[/tex], at a constant rate [tex]\alpha[/tex], with [tex]\theta = 0[/tex] at t=0, causing the particle to move down the plane.

    So, I'm taking the x to be the distance the particle travels down the slope.

    I come up with the following as the Lagrangian:

    [tex]L = \frac{1}{2} m\dot{x}^2 - mg(r-x)sin\theta[/tex]

    I'm not sure if this is correct.

    I would then get the equations of motion to be [tex]mgsin\theta - m\ddot{x}=0[/tex] and [tex]-mgsin(r-x)cos\theta=0[/tex].
    Last edited: Oct 11, 2005
  2. jcsd
  3. Oct 17, 2005 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Sorry for the late reply. In case you're still interested, here's my response to this question.

    The KE term isn't right. It should have 2 terms, and one should contain an [itex]\alpha[/itex]. The PE term is OK.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook