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!

How to find the velocity of a pendulum need help

  1. Feb 9, 2010 #1
    How to find the velocity of a pendulum...need help!!

    1. The problem statement, all variables and given/known data
    A 3.60 m long pendulum with a 1.25 kg bob is pulled sideways until it is displaced 1.80 m horizontally from its rest position. If the bob is released, calculate the speed of the bob when it is 0.250 m about it's rest position.


    2. Relevant equations

    I found the potential energy when it passes through rest position= 5.91 J
    and the velocity when it passes through rest position is 3.08 m/s. I don't know how to find it at 0.250 m & need help please!!
     
  2. jcsd
  3. Feb 9, 2010 #2
    Need help to find the velocity of a pendulum at a distance please!!

    1. The problem statement, all variables and given/known data
    A 3.60 m long pendulum with a 1.25 kg bob is pulled sideways until it is displaced 1.80 m horizontally from its rest position. If the bob is released, calculate the speed of the bob when it is 0.250 m about it's rest position.


    2. Relevant equations

    I found the potential energy when it passes through rest position= 5.91 J
    and the velocity when it passes through rest position is 3.08 m/s. I don't know how to find it at 0.250 m & need help please!!
     
  4. Feb 9, 2010 #3
    Re: How to find the velocity of a pendulum...need help!!

    I think you mean you found the kinetic energy when it passes throught the rest position this being equal to the loss of potential energy.Use the same method,find the vertical distance moved when the horizontal displacement goes from 1.8m to 0.25m and use PE lost=KE gained.
     
  5. Feb 9, 2010 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi grr_physics! Welcome to PF! :wink:
    You don't need to do that …

    just use conservation of energy (and a bit of elementary trig). :smile:
     
  6. Feb 9, 2010 #5
    Re: Need help to find the velocity of a pendulum at a distance please!!

    so do i do this:

    Ep = Ek
    mgh = 1/2mv^2
    gh = 1/2v^2
    (9.81)(0.250)=1/2v^2

    and keep going til i get the answer? where do i do trig?
     
  7. Feb 9, 2010 #6
    Re: How to find the velocity of a pendulum...need help!!

    so do i do this:

    Ep = Ek
    mgh = 1/2mv^2
    gh = 1/2v^2
    (9.81)(0.250)=1/2v^2

    and keep going til i get the answer?
     
  8. Feb 9, 2010 #7

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    That's right.

    And you'll need the trig to find the height when the horizontal displacement is 1.80 m :wink:
     
  9. Feb 9, 2010 #8
    Re: Need help to find the velocity of a pendulum at a distance please!!

    thanks! :)
     
  10. Feb 9, 2010 #9

    berkeman

    User Avatar

    Staff: Mentor

    Re: Need help to find the velocity of a pendulum at a distance please!!

    Two threads merged into one. Please do not multiple post your questions, grr.
     
  11. Feb 9, 2010 #10
    Re: How to find the velocity of a pendulum...need help!!

    sorry, promise i won't anymore!!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How to find the velocity of a pendulum need help
Loading...