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!

Length of a Closed Air Column

  1. Jan 15, 2016 #1
    1. The problem statement, all variables and given/known data
    The resonant length of a closed air column at the first resonance is 0.375m, what is the wavelength when at 4th reasonance

    2. Relevant equations


    3. The attempt at a solution
    1/4λ=0.375m
    λ=1.5m
    1.5m/7 = 0.214m
     
  2. jcsd
  3. Jan 15, 2016 #2

    Merlin3189

    User Avatar
    Gold Member

    I agree with your wavelength at first resonance and your answer.
     
  4. Jan 15, 2016 #3

    TSny

    User Avatar
    Homework Helper
    Gold Member

    As third poster, I second your fourth resonance answer.:smile:
     
  5. Jan 15, 2016 #4
    This was a question on a test, the way I got the answer was knowing v/f=λ and i knew that 7/4 of the wave fits in the 4th reasonance and 1/4 in the first, meaning the frequency is 7x more. I assumed the the velocity was 1.5m/s and the frequency was 1hz so 1.5ms/1hz = 1.5m, after that i mutliplied the 1 hz by 7 to get the answer. Is there an easier way to go about this?, I had trouble with it because the neither the speed of sound or frequency was given.
     
  6. Jan 15, 2016 #5

    TSny

    User Avatar
    Homework Helper
    Gold Member

    That's the key.

    Note that the 0.375 m given in the problem represents the length of the pipe. So 7/4 λ = 0.375 m.

    You don't need to assume a value for f.
     
  7. Jan 15, 2016 #6
    Ohhh okay I see, thank you. I knew there was an easier way to look at it.
     
  8. Jan 15, 2016 #7

    TSny

    User Avatar
    Homework Helper
    Gold Member

    Good. Drawing pictures for these types of problems is always a good thing to do.
     
  9. Jan 16, 2016 #8

    Merlin3189

    User Avatar
    Gold Member

    Absolutely agree with TSny, draw diagrams. I did.

    You may notice my first post is oddly worded, because you tricked me into thinking you'd done the second part wrongly and I had to edit it!
    I had ##\frac{λ_1}{4}=0.375## and ##\frac{7λ_2}{4}=0.375## so when I saw your /7 I thought at first you'd missed out the 4.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Length of a Closed Air Column
Loading...