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Homework Help: Harmonic motion

  1. Nov 19, 2007 #1
    1. The problem statement, all variables and given/known data

    A 171 g object on a spring oscillates left to right on a frictionless surface with a frequency of 3.00 Hz and an amplitude of 11.0 cm.
    (a) What is the spring constant?
    (b) If the object starts from rest at x = 11.0 cm at t = 0 and the equilibrium point is at x = 0, what equation describes its position (in centimeters) as a function of time (in seconds)?
    x(t) =

    2. Relevant equations

    (a) was solved and the spring constant was found to be 60.75 N/m

    (b) b) x = A cos (omega t)

    3. The attempt at a solution

    omega is 2pi*3 hZ so omega would be 6pi. Thusly, x(t) = .11 cos (6pi) t
    Am I correct? Our online homework system is not accepting my answer and I am not certain if it is because I made a mistake in physics or the syntax of my answer. Could someone verify I am right or wrong?
    Last edited: Nov 19, 2007
  2. jcsd
  3. Nov 19, 2007 #2
    you need to add phase constant to your equation.
  4. Nov 19, 2007 #3
    I got it.

    I needed to multiply out 6*pi to get its numerical value 18.85 and enclose the argument of the cosine function in parenthesis. 11cos(18.85t) worked.
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