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: Zwiebach page 148

  1. Oct 21, 2007 #1
    1. The problem statement, all variables and given/known data
    Here is Zwiebach's solution to Problem 8.6.

    Can someone explain the sentence "we do not use the equations of motion".

    I used the equations of motion and I got a completely different answer!

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 22, 2007 #2
    Show what you have done.
  4. Oct 22, 2007 #3
    Sorry. I stupidly forgot to upload the attachment. Anyway above the parenthetical that says note that we do not use the equation of motion, I used the equation of motion to get

    [tex] \delta L = \epsilon \frac{d}{dt}(\frac{\partial L}{\partial \dot{q}} \dot{q} ) [/tex]

    And the rest is totally different for me.

    So, why can I not use the equation of motion here?

    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook