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Oscillation/amplitude question

  1. Feb 19, 2008 #1
    Heres the question Im having problems solving...

    A 3.00kg block hangs from a spring with a spring constant of 200.N/m and is set into vertical oscillation. The block has a velocity of 0.900m/s upwards when the spring is stretched by 11.0 cm. Calculate the amplitude of the oscillation.

    So heres what I got...

    K=200
    m=3.00
    V=0.900
    x=0.11m
    Xm=?

    solve for Xm using this equation

    [​IMG]

    Am I doing it right?
    Help ASAP
    Thank You
     
    Last edited: Feb 20, 2008
  2. jcsd
  3. Feb 20, 2008 #2

    Shooting Star

    User Avatar
    Homework Helper

    Yes, provided the stretch is measured from the equilibrium position in which the mass hangs after being put on the spring. In this problem, that seems to be implied.
     
  4. Feb 20, 2008 #3
    but the answer I am getting is incorrect. The correct answer is 11.6cm (yes i did convert m to cm from my final answer)

    Can someone please solve this
    Thanks
     
  5. Feb 20, 2008 #4
    It may help to note that you have somehow transmuted 300 kg into 3 kg!

    Using the correct mass, the amplitude of the oscilation is 1.16 m or 116 cm - which is what is was supposed to be apart from a factor of 10? Did you mess up the decimals here as well? (No hard feelings, that happens for the best of us)
     
  6. Feb 20, 2008 #5

    Oops...sorry. It is suppose to be 3.00kg. According to the book, yes, the correct answer should be 11.6cm. Do you think you can solve it for me? Ive got a midterm today at 11.30

    Thanks
     
    Last edited: Feb 20, 2008
  7. Feb 20, 2008 #6
    Are you sure it is not 300 *grams* = 0.3 kg? In that case I get 11.5 cm, which is the best so far - otherwise I get 15.6 cm

    The general symbolic solution is pretty obvious:

    [tex]
    x_{\textrm{max}}=\sqrt{x^2+\frac{mv^2}{k}}
    [/tex]
    Which is also what you will get from a diffential-eq approach. So it is correct - It seems that you just need to get the numbers right.
     
    Last edited: Feb 20, 2008
  8. Feb 20, 2008 #7
    ok...so maybe the books answer is incorrect because I got the same answer as you
    Thanks
     
  9. Jun 21, 2009 #8

    pet

    User Avatar

    can I just check that this is the same sort of question?

    "A mass at the end of a spring oscillates with a period of 2.8s. The mazimum displacement of the mass from its equilibrium position is 16cm.

    a) what is the amplitude of the oscillations?
    b) i) its angular frequency;
    ii) its maxium acceleration.


    I've looked through most of the posts about this, and I still can't work out whether this is the same sort of question, or how to work it out. please help.
     
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