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Question
A ship in a sea sends SONAR waves straight down into the seawater from the bottom of the ship. The signal reflects from the deep bottom bedrock and returns to the ship after 3.5 s. After the ship moves to 100 km it sends another signal which returns back after 2 s. Calculate the depth of the sea in each case and also compute the difference in height between two cases.
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Solution
In the first case
time = 3.5s
Velocity sound in sea water = 1450 m/s
Distance 2d = v × t
= 1450 × 3.5 = 5,075 m
Depth of the sea d = `5075/2` = 2537.5
In the second case,
time = 2s
Velocity of sound in water = 1450 m/s
Distance 2d = vt
= 1450 × 2
= 2900 m
Depth of the sea d = `2900/2` = 1450
Difference ∆d = 2537.5 – 1450 = 1087.5
= 1087.5 m
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