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SHM - Phase Changes

  1. Jun 17, 2011 #1
    Hi,

    As part of my SHM lessons, I got this sheet today to study Phase Difference. I tried drawing what was asked and I have the impression I got the first two graphs correct. However, I am in doubt regarding the third, mostly I guess, with differentiating what is meant by ahead and behind :confused:

    Thanks,
    Peter G.

    (The drawings are really sketches until I understand their shapes properly)
     

    Attached Files:

  2. jcsd
  3. Jun 17, 2011 #2

    Doc Al

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    Staff: Mentor

    Ahead and behind don't distinguish much when the phase difference is pi.

    But your diagrams look OK.
     
  4. Jun 17, 2011 #3
    For the last one, I should really start then showing the curve at the top, correct?
     
  5. Jun 17, 2011 #4

    Doc Al

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    I don't understand what you mean. I thought that last one was for something pi/4 behind the top diagram?
     
  6. Jun 17, 2011 #5
    Yeah, that's what it asks for. So that means it starts like, an eighth of a cycle later? Do you think you could maybe draw a rough diagram on something like paint? I have a hard time conveying this kind of stuff in words :redface:
     
  7. Jun 17, 2011 #6

    Doc Al

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    The diagram would look pretty much like what you drew. It starts an eighth of a cycle 'before' the first diagram. Interpret that like this: At t = 0 the top diagram is already at the peak, while the last diagram takes an eighth of a cycle before it gets to the peak. It's behind the other.
     
  8. Jun 17, 2011 #7
    Ah ok, it's what I thought initially. Thanks a lot for your patience. :smile:
     
  9. Jun 17, 2011 #8

    Doc Al

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    My pleasure. It's tricky stuff.

    Check out the diagrams on this page; they may help. (The topic is not SHM, but the principle is the same.) http://www.allaboutcircuits.com/vol_2/chpt_1/5.html" [Broken]
     
    Last edited by a moderator: May 5, 2017
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