# Time it take to hear a stone

1. Jan 27, 2009

### ahrog

1. The problem statement, all variables and given/known data
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?

2. Relevant equations
v= wavelength x frequency

3. 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...

2. Jan 27, 2009

### 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/Vsound

3. Jan 28, 2009

### 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?

4. Jan 28, 2009

### rl.bhat

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