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Find Frequency and Amplitude from Max Velocity and Accn

  1. Jan 25, 2013 #1
    1. The problem statement, all variables and given/known data
    See attached screenshot


    2. Relevant equations
    Vmax=Aω
    ay=-ω2A

    3. The attempt at a solution
    The given max velocity is 1.2 m/s, so

    1.2 = ωA

    Ay = -ω^2A

    1.2/A = -√260/A
    A = 0.005
     

    Attached Files:

  2. jcsd
  3. Jan 25, 2013 #2

    haruspex

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    Parentheses would help, and don't worry about the sign because you only want the magnitude.
    A little inaccurate. How many significant figures do you think you should provide?
    This is just part B. Any problem with part A?
     
  4. Jan 25, 2013 #3
    I tried 0.006, but it didn't work either. I am not sure what to do for part A at all.
     
  5. Jan 25, 2013 #4

    haruspex

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    You didn't answer my other question: how many significant figure do you think you should give in the answer? Why are you only giving one?
    You already have an equation you can solve for ω.
     
  6. Jan 28, 2013 #5
    There should be two significant figures, but my homework doesn't mind a little inaccuracy. I'm still having difficulty with part A.

    Since

    A = (ω)/(vmax)

    and

    A = (amax)/(ω2)

    then

    ω/vmax = amax/(ω2)

    Plug in knowns:

    260/(ω^2) = ω/1.2
    ω3 = 312
    ω = 6.78
    ω = 2πf
    f = 1.08

    This is not correct, though. And I do not know why.
     
  7. Jan 28, 2013 #6

    haruspex

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    OK, but I think it's worth trying 0.0055
    No - try that one again. (What dimension would frequency/speed have?)
     
  8. Jan 29, 2013 #7
    0.0055 was incorrect.

    frequency/speed would be m/sec^2... OH!

    So A = (vmax)/ω, correct?
     
  9. Jan 29, 2013 #8

    haruspex

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    Yes.
     
  10. Jan 30, 2013 #9
    I'm still getting 0.0055 for amplitude. Any ideas?
     
  11. Jan 30, 2013 #10

    haruspex

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    0.0055m looks right to me.
     
  12. Jan 30, 2013 #11
    Well the homework software is counting it wrong. Thanks for the help!
     
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