1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Wave Questions

  1. Dec 1, 2005 #1
    Hey guys i've got a few questions I didn't know how to do and would appreciate if you could help me out...

    A wave generator is used to produce transverse waves in a string that is 12 metres long. Initially, the wave generator is set to a frequency of 5.0 HZ

    a) How many wavelengths are being created each minute by the wave generator? (Hint: how many in one second?)

    b) What is the period of the wave being gnerated?

    c) If the speed of a wave in the string is known to be 15 m/s, what is the length of one wave?

    d) The frequency of the wave generator is now changed so that it produces a standing wave pattern along the string. An observer counts 3 nodes along the entire length of the string. What is the frequency of the wave generator when it is producing this standing wave?

    I am aware that frequency and periods are inversly related

    T = Period
    f = frequency

    Therefore: T = 1/f & f=1/f


    equations we are given to use are:

    v= d/t & v=f(wavelength) (velocitiy equals frequency times wavelength.)

    Would love some help..

    Thanks in advance.
  2. jcsd
  3. Dec 1, 2005 #2


    User Avatar
    Homework Helper

    Did you answer the hint question? If there are 60 seconds in 1 minute, how many seconds are in 1 hour? If there are X waves in 1 second, how many waves are there in 1 minute?

    Part b won't be a problem since you have your equations there.

    Part c as well ^^

    Part d is a standing wave situation. The generator must be generating at the wire's resonant frequency. You'll have to assume that the other end is a fixed end. It's easier to start from finding the resonant wavelength of the third harmonic, or do you remember the equations for this?
  4. Dec 1, 2005 #3
    in question a would the answer be?

    5 cycles/second = 60 s * 5 cycles/s = 300 cycles a minute
    Therefore in question a the wave machine would generate 300 wavelengths per minute

    b) T=1/f T=1/5hz T=0.2 seconds Therefore the period is 0.2 seconds

    c) I am not exactly sure which equation to use here v=d/t or v=f*(wavelength)

    d) I still am unsure of how to start this
  5. Dec 1, 2005 #4


    User Avatar
    Homework Helper

    If your calculations are logical, be a bit more confident in your answers ^_^

    c. What two variables do you have? velocity, frequency, wavelength, distance, time. Pick the right one that would solve.

    d. I wouldn't want to give you an equation if you don't know what it means. You can read http://www.cord.edu/dept/physics/p128/lecture99_35.html#topic3

    You're looking at a case where one end is open (movable) and the other end is fixed.
  6. Dec 1, 2005 #5
    I think I'll leave d and go for help for that tomorrow

    its just c

    v= 15m/s
    d=? asked to find
    wavelength= 300?

    if I use v=d/t for question c) then d=t*v

    it doesn't work

    ..... v=f times wavelength then:
    wavelength = v/f

    wavelength = 3m? ^_^
    Last edited: Dec 1, 2005
  7. Dec 1, 2005 #6


    User Avatar
    Homework Helper

    The equation d = vt should not be new to you. You use it every day in life. If you are driving at 100 miles/hr and going to a nearby city 200 miles away, how long will your journey be? Surely you can figure that out.

    The equation [tex]v = f \lambda [/tex] can be shown similarly. If you know the wavelength and frequency of the wave, you can find its velocity. Or if you know any 2 of the 3. From your last three lines, I think you have an answer ;)
  8. Dec 1, 2005 #7
    i know the v=d/t quite well...its just which to use with each variable...

    I understand c.

    I would like to thank you for the help once again.

    Keep the blue side up.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Wave Questions
  1. Wave question (Replies: 1)

  2. Waves question (Replies: 1)

  3. Wave Question (Replies: 6)

  4. Waves Question (Replies: 1)

  5. Waves question (Replies: 6)