Solving Submarine Problem - Alex

[Vanity]

Hi,

I need to solve this problem but I have no idea where to start. I made a little drawing with all the informations I have but now I'm stuck. Here's the problem:

A submarine uses sonar waves, to identify other ships, by directing a highly directional acoustic pulse at a target, and computing the time duration between the transmission of the "ping", and the return of the echo. If a sub is a depth of 500m and receives a ping return in 5.6s, determine the direct distance to the ship.

I'm not looking for the answer, just a little hint of what to start with. Thanks a lot !

- alex.

 

[Doc Al]

What's the speed of sound in water? How far must the sound have traveled in 5.6s? (Don't forget that the sound makes a round trip.)

 

[Vanity]

Great ! Thanks. One last question, does the temperature affects anything ? Thanks !

 

[Doc Al]

Both pressure and temperature will affect the speed of sound. (But I'll bet you can ignore such complications.)

 

[Vanity]

The problem actually include the temperature, so I guess I need to include it in my formula. I google'd for it but could only find tables. If density of water is 1, what formula should I use ?

Thanks !

 

[Doc Al]

Unless this problem is meant to exercise your detailed understanding of the speed of sound in a liquid (the speed depends on the bulk modulus and density, which in turn depend on pressure and temperature), I would just look up the speed of sound (in seawater... salinity counts!) at some standard temperature. That should be good enough.