## YumYum247 one year ago yelp!!!

1. YumYum247

2. YumYum247

This is how i attempted to do the question..... Fn = nF1 (16.5Hz) Fn = 16.5Hz The fundamental frequency is 16.5Hz

3. YumYum247

can someone please give me a hint on how to solve for the speed of the wave...V = d/t How do i find time here?????????????? :(

4. YumYum247

|dw:1436754247641:dw|

5. Astrophysics

$v = \lambda f$

6. Astrophysics

What did you get for the first answer?

7. YumYum247

the fundamental frequency/natural frequency of the string is 16.5Hz

8. Astrophysics

But it's asking for the string

9. Astrophysics

$\huge f_{freq} = 3 f_{string}$

10. Astrophysics

Where your $f_{freq} = 16.5 Hz$

11. YumYum247

fundamental frequency is the lowest frequency that a system can produce to make a standing wave.

12. YumYum247

that would the natural frequency in the 3rd harmonic phase.

13. YumYum247

i did a question earlier related tho this, and the fundamental frequency of the wave was the very lowest that a wave produced in a fixed postion....like this |dw:1436755214463:dw|

14. YumYum247

that is the fundamental frequency of the wave....F = 30/.20 = 150Hz So the other two frequencies i had to figure out that make the standing waves were.... Fn = nF2 Fn = F2(150) = 300Hz Fn = nF3 Fn = F3(150) = 450Hz

15. YumYum247

|dw:1436755541130:dw|

16. YumYum247

|dw:1436755603442:dw|

17. YumYum247

|dw:1436755633977:dw|

18. YumYum247

but how do i find the time of wavelength?????????????:/

19. YumYum247

@mathmate

20. YumYum247

@pooja195

21. IrishBoy123

*can someone please give me a hint on how to solve for the speed of the wave* its a standing wave and its wave form is not actually visibly *travelling* but it still has "velocity" $$v = \frac{2 \ L \ f_n}{n}$$ so velocity $$v$$ and freq $$f_3$$ for the 3rd harmonic are related as follows: $$v = \frac{2 \ L \ f_3}{3}$$ or $$f_3 = \frac{3v}{2L}$$

22. YumYum247

Thank you Irishman!!! :)

23. YumYum247

and is my fundamental frequency correct?????????????????? @IrishBoy123

24. IrishBoy123

this is a long old thread so let me step through it as i see it and you judge if this makes sense to you: first there is resonance with the 16.5Hz source so we can say: |dw:1436805378856:dw| v is fixed, it is a consequence if the tension in and density of the string. so the "fundamental harmonic will look like this: |dw:1436805640680:dw| if this makes sense, we can do the last bit and look again at that equation i posted as i think it is important to note that it is totally derivable and not something of a lack box. this fits nicely with part (iii) of the question so i hope this is all going according to plan.....

25. IrishBoy123

forgive "lack box" [= "black box"] and myriad other typos....

26. IrishBoy123

in terms of what can be a resonant frequency, here is the beginning of the possible standing wave patterns: |dw:1436806502148:dw| IOW: $$\lambda_n = \frac{2 L}{n}$$ and $$v = f . \lambda$$ which gives us the formula i quoted previously, $$f_n = \frac{v}{\lambda} = \frac{n . v}{2L}$$ ergo, resonant frequencies go in integer multiples of $$\frac{ v}{2L}$$ which here is $$\frac{66}{2*6} = 5.5Hz$$. and $$\frac{28.5}{5.5} = ???$$ does that make sense to you? do you agree?

27. YumYum247

|dw:1436844986642:dw|

28. YumYum247

|dw:1436845232173:dw|

29. YumYum247

f1 = 5.5Hz and V = 66m/sec

30. YumYum247

The next question asks me to find whether or not the new frequency of 28.5Hz would make a standing wave on the spring??????And this is how i did it.......|dw:1436847792123:dw|

31. YumYum247

|dw:1436847968394:dw|

32. YumYum247

i think in order for the new frequency to produce a complete standing wave, it has to be twice as big as the fundamental frequency....in this case 33Hz to make the next standing wave on the string......am i right???????O-o

33. YumYum247

@IrishBoy123 @Astrophysics the question asks me to find the minimum length of air in a column required for resonate??????This is how i did it...please check my work :)

34. YumYum247

|dw:1436850740578:dw|

35. YumYum247

|dw:1436851048790:dw|

36. YumYum247

is that the minimum length of air/ fundamental length of air????????

37. YumYum247

@Michele_Laino Can you please check my work??????

38. YumYum247

the question asks me to find the fundamental frequency....i've done it up there but no one bothered to check my work, could you please give me a hand here???

39. Michele_Laino

I'm very sorry, I don't know your answer, since in my physics courses I have not studied acoustics

40. YumYum247

Aawwnnnn!!! :(

41. YumYum247

@Elsa213

42. Elsa213

@dan815

43. Elsa213