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: Oscillary Motion

  1. Nov 11, 2004 #1
    The Problem is:
    A particle executes simple harmonic motion with an amplitude of 2.25 cm. At what position does its speed equal half its maximum speed?

    I've been looking at this for a while, and I cant see how to solve it without more information.

    If I knew the energy and mass I could solve it,
    if I knew the frequency or period I could solve it,
    if I knew the spring constant and mass I could solve it,
    but I dont have any of this, what's the trick?
  2. jcsd
  3. Nov 11, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper

    HINT: For what value of z does cos z equal half its maximum value?
  4. Nov 11, 2004 #3


    User Avatar
    Homework Helper

    Use symbols instead of numbers.

    The position of the particle x=Asin(wt), A= 2.25 cm.
    The velocity of the particle v= Awcos(wt).
    The maximum velocity is Aw.
    You look for the position when v=0.5 Aw.
    0.5 Aw = Aw cos(wt) ----> cos(wt)=0.5.

    You only ned to find sin(wt) to get x.

  5. Nov 12, 2004 #4
    You can apply the general velocity formula for SHM here. since maximum velocity is v=rw, then take the half of it and equal to general formula. Work it out and you should be able to find the positions.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook