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Homework Help: Sinusodial waves and nodes

  1. Mar 29, 2016 #1
    1. The problem statement, all variables and given/known data
    Two sinusodial waves, each of wavelength 5m and amplitude 10cm, travel in opposite directions on a 20m streched string which is clamped at each end. Excluding the nodes at the ends , how many nodes appear in the resulting standing wave?
    2. Relevant equations

    3. The attempt at a solution

    So I just drew a picture, 20m long string, and drew a wave through it with each wavelength being 5m. I basically disregarded that there were two separate waves. I still got the right answer. Is the fact that they collide irrelevant? Why?
  2. jcsd
  3. Mar 29, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    It is only irrelevant once proved to be so.
    Consider an instant at which the two waves reinforce to the maximum extent at some point. Drawa picture of this. Draw the two individual waves on the same picture. Do they reinforce everywhere at that time? Compare the nodes of the three waves.
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