How Long Does It Take to Hear a Stone Hit the Bottom of a Shaft?

[ahrog]

Homework Statement

Someone drops a stone into a mine shaft 122.5 m deep. How soon after she drops the stone does she hear it hit the bottom of the shaft?

Homework Equations

v= wavelength x frequency

The Attempt at a Solution

I changed the equation to be:
d/t=wf
t=d/wf
t=122.5m/(343m/s x f)

And I'm stuck there...I don't get how to get the frequency

My textbook doesn't even refer to something like this, so I'm extremely confused...It's like asking someone about something they've never learned before...

 

[LowlyPion]

First you need to figure the time for it to fall 122.5m, then add the time for the sound to return.

Δt = D/V_sound

 

[ahrog]

I got the falling part time to be 5 seconds.

And for the time for the sound to return, how do I figure that out? If the velocity for the sound is wavelength x frequency which I have only the wavelength, how can I find the time?

 

[rl.bhat]

t=122.5m/(343m/s x f)
Here f in not needed. time = distance/velocity.