need physics help!!

[Omegachi]

help meeeh! i need to know how to do this problem for my final.... i can't get it towork out!!@#!@#



1. You drop a vibrating 440 Hz tuning fork down an old mine shaft and the last frequency you hear is 400 Hz as the sound fades. The speed of sound in air is 340 m/s.
a) What is the speed of the tuning fork when you last hear it? (answer: 34m/s)
b)How deep was the fork when it emitted the sound at 400Hz? (answer:58.92m)
c)How deep was it when you heard the sound? ( answer:65m)

~~~for this problem i know it involves the dopplershift(which is the dopplershift equation?). and for part c) think that its asking how how is it after emiting the sound and falling a distance 'y'

please try to work out as much steps as possible.... i

 

[zzzz]

you need to open a book and read the doppler effect. The equation will be there. This is not a trick question. simple if you get the formula.

 

[Omegachi]

still not sure which one...

f'=1/(1+- (u/v)) fo ?

whats the U and v? is the v the speed of sound in air?

 

[lawaris]

think of a reference point/frame from where to measure the vel. and then u will get the sign of the vel. correct

 

[Omegachi]

so thats the right formula?

 

[Jittles]

There should be seperate doppler shift equations. 4 to be exact.

2 for source moving
2 for listener moving

find the one where the source is moving away and use that. The book should tell you what each variable means.

part c is just asking when it is falling at such a speed that the sound you hear is less than 20 Hz (audible limit), how far down is it?

 

[Omegachi]

hmm....got everything else but part c

do i use Vf^2 = -2g (delta Y)?