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Homework Help: Find Acceleration At Time t For Mass on a Spring

  1. Dec 4, 2011 #1
    The problem statement, all variables and given/known data
    A mass is oscillating on a spring with a period of 4.35 s. At t = 0 the mass has zero speed and is at x = 3.25 cm. What is the magnitude of the acceleration at t = 1.30 s?

    The attempt at a solution

    The formula for oscillatory acceleration is
    a(t) = -Aω^2cos(ωt - ∅)
    a(x) = -(ω^2)x

    ω = 2pi/period, which is 2pi/4.35

    So,

    a(t) = -(2pi/4.35)(3025cos((2pi/4.35)(1.30)))
    a(t) = 0.6798 m/s^2

    This isn't the correct answer.

    The question states that it starts at t= 0 at x=3.25, so I took that to be A. Is that my problem? Where am I going wrong?
     
  2. jcsd
  3. Dec 4, 2011 #2
    Check your arithmetic. I assume 3025 is actually 3.25. Secondly, you are not evaluating the formula you cite.
     
  4. Dec 4, 2011 #3

    Doc Al

    User Avatar

    Staff: Mentor

    OK.
    Redo this.
    That makes sense to me. (Be sure to use standard units for distance.)
     
  5. Dec 4, 2011 #4
    I have the answer now. Thank you!
     
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