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How to find wavelenght of a 3m spring with 2,5 Hz?

  1. Sep 8, 2014 #1
    Hi! I just can't figure this out.

    A 3m long spring makes transverse waves with a 2,5 Hz frequency. What is the wavelength?

    I don't even know where to start, because in out incredible small physics course, we never learned this. :)
     
  2. jcsd
  3. Sep 8, 2014 #2
    Are these all the data you have? Does it say if the spring is fixed at its ends? Does it say if it's the fundamental armonic?
     
  4. Sep 8, 2014 #3
    Thats all the info. The only formula have have learned is λ = v/f, and that won't work here after what I can see. There are four options after the question:

    a) 0.67m
    b) 3.75m
    c) 1.5m
    d) 6m
     
  5. Sep 8, 2014 #4
    All right, then I think you have to assume that the spring is fixed at both its ends. Then you have a formula that states that only some particoular waves can occour in that spring (its armonics). Have you ever heard or seen this formula?
     
  6. Sep 8, 2014 #5

    BvU

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    Hello Konto, and welcome to PF. There must be more to this. Is there a preceding question that is continued in this one ?
    If you can't find anything there, all I can advise is to look up (google) images of standing waves and see if you get some inspiration there....
     
  7. Sep 8, 2014 #6
    you should check out other data that they gave you. This way, it's just impossible to understand. :)
     
  8. Sep 8, 2014 #7
    First of all, sorry for not using the right template etc. when posting this topic. I will do better in future topics.

    I have never heard about any other formula for finding wavelength than λ = v/f. We don't even have a book in physics, all the info we need is in a 75 page long compendium that the teacher made for the 6 week course, and the compendium never mentions such a formula.

    This was the first question. :( I found a picture that was suppose to go with the question (didn't get printed). Maybe that can help?
     

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  9. Sep 8, 2014 #8
    Yes the picture is extremely useful because tell us that the spring is fixed at its end and the wave is its fourth armonic. There are a lot of beautiful videos that could help you understandig what we are talking about: try searching on YouTube stationary waves.
    The formula anyway says that [tex] \lambda = \frac{2L}{n} [/tex] where L is the length of the spring and n the number of the armonic.
    It's an interesting stuff, expecially if you are interested in music, so I suggest you to try to understand it on your own, or even better ask your teacher for some useful sources :)
     
  10. Sep 8, 2014 #9
    Well thats great news, thank you so much. :) Now I'll just have to ask the teacher why he would make a question that we never could figure out if we only look at the compendium. :)
     
  11. Sep 8, 2014 #10

    BvU

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    Looks as if you can now answer the question by just looking at the picture: how many wavelengths do you see ?
     
  12. Sep 8, 2014 #11
    Wow, I did not realize that. :) Thanks for opening my eyes. :)
     
  13. Sep 8, 2014 #12

    BvU

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    Just to be sure I didn't wrong-foot you: what is your conclusion?
     
  14. Sep 8, 2014 #13
    λ = 2*3m/4 = 1,5m :)
     
  15. Sep 8, 2014 #14

    BvU

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    Looks like the right answer to me !
     
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