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!

Find the equations of the trajectories?

  1. Feb 12, 2015 #1
    1. The problem statement, all variables and given/known data
    Find the equations of the trajectories of y"+y^3=0.

    2. Relevant equations
    None.

    3. The attempt at a solution
    The Undamped Case:
    y"+p(y)=0
    v(dv/dy)+p(y)=0
    integrate
    v^2/2+P(y)=C
    ---------------------------------
    So following the formula above:
    The answer I got is v^2/2+y^4/4=C, but the answer in the book says v^2+y^4/4=C. What's wrong?
     
  2. jcsd
  3. Feb 12, 2015 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Did you, blindly, followed a formula?

    What makes you think the formula applies in this case?
    Did you follow the formula correctly?
    Did you check your algebra?
    Did you check your arithmetic?

    Maybe the book made a typo?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted