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!

Pendulum without oscillation

  1. Oct 20, 2005 #1
    If a mass (m) at the end of a length (L) on a pendulum starts at an angle of θ from the vertical, what is the minimum inital velocity v0 it must have to just barely make it over the top and not oscillate?

    This is what I did:

    [tex]\Delta K=mgh\implies v_0=\sqrt{v^2-2gh}[/tex]

    but at the top, v is zero so it can be written as:


    and h in this case is L+Lcosθ, so using g=-10m/s2 I get:


    but whenever I plug in values for θ and L, I get the wrong answer. I can't see what I did wrong.

    Any ideas?

    Thanks a lot.
  2. jcsd
  3. Oct 20, 2005 #2
    What School do you go to?
  4. Oct 20, 2005 #3
    I'm in high school.
  5. Oct 21, 2005 #4


    User Avatar
    Science Advisor

    At the top the pendulum has 0 velocity (actually, it should have just a tiny non-zero velocity but you can take 0 as "boundary" between going over the top and not making it to the top) and so has no kinetic energy but has potential energy, -mgL (relative to the height of the pivot- the center of the circle the pendulum moves in). Initially, it has velocity v0 and so kinetic energy (1/2)mv0[/sub]2 AND some potential energy. Have you taken into account the fact that the potential energy has to be measured with respect to the center of the circle?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Pendulum without oscillation
  1. Pendulum oscillation (Replies: 5)

  2. Pendulum Oscillations (Replies: 9)