Posted by **Kristina** on Friday, February 11, 2011 at 3:12pm.

At a height of 15 meters above the surface of a lake, a sound pulse is generated. The echo from the bottom of the lake returns to the point of origin 0.150 s later. The air and water temperatures are 20°C. How deep is the lake?

- Physics -
**Damon**, Friday, February 11, 2011 at 3:50pm
look up speed of sound in water at 20C

call it Cw

look up speed of sound in air at 20C

call it Ca

then distance in water = 2d

distance in air = 30

time in water = t

time in air = (.15 -t)

then

time in air = 30/Ca = .15 - t

solve for t

then

Cw t = 2 d

- Physics -
**SraJMcGin**, Friday, February 11, 2011 at 4:50pm
Try some of the Physics Tutorials:

http://search.yahoo.com/search?fr=mcafee&p=Physics+tutorial

Sra

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