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!

Central Force

  1. Dec 12, 2007 #1
    1. The problem statement, all variables and given/known data
    A particle moves under the action of a central force in a spiral orbit given by r=a*theta. Show that the force is f(r) = (-L^2/mr^3)*[1 + (a^2)/(r^2)]


    2. Relevant equations



    3. The attempt at a solution
    I know how to do the problem, but I keep ending up with a factor of 2 for the a^2 term. Any pointers on how to fix this? Thanks for the help!
     
  2. jcsd
  3. Dec 12, 2007 #2

    Kurdt

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If you post exactly what you've done, people will have a better idea of what mistakes you may have made.
     
  4. Dec 12, 2007 #3
    Sorry for that.... I used the equation d^2u/dtheta^2 + u = (-1/ml^2u^2)*f(u^-1). For the second derivative of u with respect to theta i got 2*a*theta^-3, which i re-wrote as 2*a^2*u^3. I plugged that result into the diff. equation, but was unable to 'get rid of' the factor of 2 for the a^2 term. Any pointers?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Central Force
  1. Central Force (Replies: 2)

  2. Central force (Replies: 2)

  3. Central force (Replies: 18)

  4. Central Forces (Replies: 11)

Loading...