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A problem on tuning fork.

  1. Jan 30, 2017 #1
    1. The problem statement, all variables and given/known data
    2 tuning forks A and B, when sounded together produce 4 beats. when B is loaded with wax, the beat frequency remains same. if frequency of A is 212 Hz, then frequency of B is?

    2. Relevant equations
    beat-frequency-formula.PNG

    3. The attempt at a solution
    since the beat frequency is 4 and frequency of A is 212 Hz, the frequency of B should be either 216 or 208. B is waxed which means it's frequency is decreased. if we assume the frequency of B as 216, on waxing the beat frequency decreases and considering the latter, waxing increases the beat frequency. but in the given question, it says beat frequency remains same.how could i solve this?
     
  2. jcsd
  3. Jan 30, 2017 #2

    DrClaude

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    Staff: Mentor

    Will the beat frequency always decrease, however much wax is added?
     
  4. Jan 30, 2017 #3
    i guess so. doesn't it?
     
  5. Jan 30, 2017 #4

    DrClaude

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    What happens if I add enough wax to get the frequency of B below 212 Hz?
     
  6. Jan 30, 2017 #5
    sorry.i don't get you
     
  7. Jan 30, 2017 #6

    DrClaude

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    How does the beat frequency varies with the amount of wax as I add enough wax to get B vibrating at less than 212 Hz?
     
  8. Jan 30, 2017 #7
    the beat frequency will go on increasing, if the frequency of B is constantly becomes lesser than 212
     
  9. Jan 30, 2017 #8

    DrClaude

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    Correct. You should now be able to answer the problem.
     
  10. Jan 30, 2017 #9
    they have given that the beat frequency remains constant even after waxing, thats where i'm confused!
     
  11. Jan 30, 2017 #10

    DrClaude

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    It is not that the beat frequency is constant, but the beat frequency with and without the wax is the same, for the particular amount of wax added.
     
  12. Jan 30, 2017 #11
    Gosh, it's hard to coach this kind of a question without just giving away the answer. Maybe just study the formula for the beat frequency a lot harder, and the answer will come.
     
  13. Jan 30, 2017 #12
    so the frequency of B is 208 Hz?
     
  14. Jan 30, 2017 #13

    DrClaude

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    With or without the wax?
     
  15. Jan 30, 2017 #14
    without the wax.
     
  16. Jan 30, 2017 #15

    DrClaude

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    If B is 208 Hz without the wax, how will the beat frequency change when wax is added?
     
  17. Jan 30, 2017 #16
    oh! if 208 Hz is waxed, then the beat frequency will be increased!
     
  18. Jan 30, 2017 #17

    DrClaude

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    Yes. So what is the answer?
     
  19. Jan 30, 2017 #18
    216Hz? is the answer?
     
  20. Jan 30, 2017 #19

    DrClaude

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    What do you think? Does it explain the observed behavior of the tuning forks?
     
  21. Jan 30, 2017 #20
    yes cause if 216 Hz is frequencyof B without loading, it makes 4 beats with A. then on loading the frequency of B decreases to 208 Hz and in this case also it makes 4 beats with A. so 216 Hz should be the frequency of B before loading. right?
     
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