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Homework Help: Simple Harmonic Motion - whats the displacement of the mass

  1. May 8, 2010 #1
    1. The problem statement, all variables and given/known data
    A mass on a spring obeys SHM.Given that the mass is initially at the equilibrium position,has an initial velocity of 2m/s,and a nastural frequency of 2 rad/s,Find A and φ
    After 13.2 sec whats the displacement of the mass

    2. Relevant equations
    ψ=Αcos(ωt+φ)


    3. The attempt at a solution
    Is the initial velocity ,the maximum velocity ? Maybe yes. Is the initial phase (φ) zero ? I think so.
     
  2. jcsd
  3. May 8, 2010 #2
    the initial velocity IS the maximum velocity, at equilibrium, KE = max, PE = zero.

    if you use your notation for the motion of the mass, ie the cosine term, then no, the phase is not zero, it has to be pi/2, because at T=0, psi must be zero because the mass is at equilibrium.
     
  4. May 8, 2010 #3
    Thanks
    Problem solved :)
     
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