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Harmonic motion with a spring question

  1. Feb 23, 2012 #1
    A 0.1-kg mass is attached to a spring having a spring constant 3.6 kg/s^2. The system is allowed to come to rest. Then the mass is given a sharp tap, imparting an instantaneous downward velocity of 0.4 m/s. If there is no damping present, find the amplitude A and frequency ω of the resulting motion.

    A) Let x=0 be the position of the spring before the mass was hung from it. Find x(0).

    If x(t) is the displacement, then wouldn't x(0) = 0 since this is before the mass was hung from it?

    B) Solve this initial value problem and plot the solution.

    Once I figure out A, I am sure I can do B.
  2. jcsd
  3. Feb 23, 2012 #2


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    Hi Norm850! :wink:

    I think they mean that x(0) is the equilibrium position after the mass is hung from it (and therefore at t = 0 when the mass is tapped).

    Find x(0) by balancing the weight down against the spring force up. :smile:
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