Graphing sound waves at the bottom of the ocean

[MyNewPony]

Homework Statement

Ships measure the distance to the ocean bottom with sonar. A pulse of sound waves is aimed at the ocean bottom, then sensitive microphones listen for the echo. The graph shows the delay time as a function of the ship's position as it crosses 60 km of ocean.

Draw a graph of the ocean bottom. Let the ocean surface define y = 0 and ocean bottom have negative values of y. This way your graph will be a picture of the ocean bottom. The speed of sound in ocean water varies slightly with temperature, but you can use 1500 m/s as an average value.

http://session.masteringphysics.com/problemAsset/1071083/10/20.P46.jpg

Homework Equations

v = d/t

The Attempt at a Solution

I'm not how to interpret the graph given. Do the time values represent how long it takes for the waves to get to the bottom? Or do they represent how long it takes for the waves to reach the bottom and echo back?

 

[LowlyPion]

Or do they represent how long it takes for the waves to reach the bottom and echo back?

Doesn't it say:

A pulse of sound waves is aimed at the ocean bottom, then sensitive microphones listen for the echo.

 

[nlightner]

If it is the latter, then the distance from the ship to the ocean bottom can be calculated by multiplying the time by the speed of sound in water. This would result in a graph with negative values for y, as instructed. However, if it is the former, then the graph would show the distance from the ship to the ocean bottom directly, with no need for calculations. Either way, the graph would show a gradual decrease in the distance as the ship moves across the ocean, indicating a gradual sloping of the ocean bottom. The varying time values could also indicate changes in the depth of the ocean bottom, as the ship may encounter different types of terrain or structures along its path. Additional data and measurements would be needed to accurately determine the shape and features of the ocean bottom.