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Find the position of a pendulum as a function of time?

  1. Feb 17, 2016 #1
    1. The problem statement, all variables and given/known data
    How do you find the position of a pendulum as a function of time?

    Mass of bob: 2.0kg
    String length (l): 3.0m

    The pendulum is displaced as a distance of 0.35m from the equilibrium point and is then released. After 100 swings the maximum displacement of the pendulum has been reduced to 0.15m.

    2. Relevant equations

    Period (T) of a pendulum: T = 2π√(l/g)

    3. The attempt at a solution
    The answer to the problem is f(t) = 0.35cos(1.81t) but I am not understanding how the 0.35 or the 1.81t is coming into play because I figured that if the angle is the point where the equilibrium point and the place where the pendulum is attached to a wall then the 0.35 would be opposite of this angle, not the adjacent of hypotenuse of the triangle created from the displacement of the pendulum. I also figured that the 0.35 was what the displacement was and I do not understand where the 1.81 came from at all.
  2. jcsd
  3. Feb 17, 2016 #2
    I have had an epiphany so moderators can lock this thread.
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