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Homework Help: Waves and Energy transfer problem ( am desperate)

  1. Apr 11, 2005 #1
    Waves and Energy transfer problem (plz am desperate)

    Well, this is the problem that is breaking my head

    the time needed for a water wave to change from the equilibrium level to the crest is 0.18s
    a) what fraction of a wavelength is this?
    b)what is the period of the wave?
    c)What is the frequency of the wave?

    I dont really understand this problem because of the little information they give me, and the fact that when i tried to check it with my brother's answer book, the wavelength gave 1/4, but they do not give a formula or say why the WL is 1/4..

    Please help me... :cry:
     
  2. jcsd
  3. Apr 11, 2005 #2
    A) Think a little, the whole wavelength would be measured from crest to crest. Let us use the sine wave as an example going from 0 to [tex]2\pi[/tex]. Compare the distance from where the function equals zero (in your wave example, this is the equlibrium point) to where it equals 1 (again, in your example the crest) and then campare it to the entire wavelength of the function.

    B) If it takes 0.18 seconds for one fourth of a wavelength to travel, how long does it take the whole wavelength?

    C) Frequency is the inverse of the time, [tex]f=1/T[/tex].
     
  4. Apr 12, 2005 #3

    HallsofIvy

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    Draw a picture! A wave starts from 0, goes up to its highest point, back down to 0, then down to its lowest point, then back up to 0: four sections, each of the same length- the whole thing is one wave length. Since you given ONE of the 4 sections (from 0 up to its highest point) you are given 1/4 of the entire wavelength.

    Since 1/4 of the entire wavelength takes 0.18s, the entire wavelength will take
    4(0.18)= 0.72 s, the period of the wave.

    As theCandyman said, the frequency is 1 over the period: 1/0.72 "cycles per second"
     
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