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Destructive Interference with Different Wave Shapes

  1. Dec 4, 2005 #1
    Here is the question

    An upright square pulse and an inverted triangular pulse were directed toward each other on a spring, as shown in the illustration. Sketch the appearance of the spring at the instant the two pulses met and completely overlapped. What principle did you use in constructing the shape of the spring for the instant at which the two pulses met? What does this principle state about how waves combine?

    i couldnt get the picture in but i think the questions explain it enough

    I am assuming the triangle and the square have the same base and height length. I know a triangle is bh\2. Therefore it is smaller than the square. Does this mean the sqaure takes over the triangle like this:

    a small square above the string.

    What principle is this

    Last edited: Dec 4, 2005
  2. jcsd
  3. Dec 4, 2005 #2


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    Gold Member

    I'm sorry I have difficulty understanding your drawings, but I believe that what is going on is that you have two pulses on a tight spring traveling towards one another. I believe the word you are looking for to describe the method you would use to sketch the solution is "superposition". This principle says that you can simply add the contributions of each pulse at every point to get the total solution. So what you've got to do is add the height of the triangle to that of the square. Since the hiegts have opposite signs they will tend to reduce each other rather than reinforce each other.
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