Tuesday
May 21, 2013

# Homework Help: Physics HELP!

Posted by Ella on Thursday, October 2, 2008 at 1:51pm.

A mountaineer estimates the depth of a crevasse by dropping a stone and listening for sound when the stone hits the bottom. The speed of sound in air is 340m/s. If the sound is heard 10s after the stone is dropped, what is the depth of the crevasse?
Do you find velocity first? i could not find any equation where i would only have one unknown for this question. please help?

• Physics HELP! - bobpursley, Thursday, October 2, 2008 at 2:02pm

break up the journey in going down, sound coming up.
Let tf be the time of fall. Then 10-tf is the time of the sound going up. In both cases, the distance is the same.

df=1/2 g tf^2
ds=vs*(10-tf)
Now, set ds=df, and solve for tf.

Once that is determined, you can find df.

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