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Which diagram below best representsthe shape ofthe rope when both puls

  1. Apr 22, 2013 #1
    1. The problem statement, all variables and given/known data

    The diagram shows two pulses, each of length , traveling toward each other at equal speed in a rope

    Which diagram below best represent sthe shape ofthe rope when both pulses are in region AB?

    2. Relevant equations



    3. The attempt at a solution

    The answer is the last option, it will be a flat line

    but this looks like constructive to me, meaning they should add up since they are the same when approaching...

    greatly appreciated if someone can explain with a diagram ,thanks


    And same as #73, i should dont know how to picture how these things work ...
     

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    Last edited: Apr 22, 2013
  2. jcsd
  3. Apr 22, 2013 #2

    CWatters

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    Initially the two +ve peaks collide and you do indeed have constructive interference and a +ve peak twice the height BUT when that happens the two waves only overlap by λ/2 and they aren't entirely within the region AB.

    The +ve peaks continue past each other until the +ve peak of one overlaps with the negative peak of the other and you get destructive interference and a flat line. At this point both waves are within AB. So flat line is the answer.

    If you let the clock run further the waves keep going until the -ve part of one overlaps with the -ve part of the other. You get constructive interference again only this time a -ve peak twice the height forms. Again this happens when they overlap by λ/2 and they aren't entirely within the region AB.
     
    Last edited: Apr 22, 2013
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