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Quick speed of sound question?

by whatwhat11
Tags: sound, speed
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whatwhat11
#1
Dec20-12, 06:14 AM
P: 14
A swimmer sees a parachutist hit the water and hears the impact twice, once through the water and the second time through the air, 1.0 s later. How far from the swimmer did the impact occur?
Vs air = 340 m/s Vs water = 1400 m/s the answer is 450m

I don't understand what to do
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Chestermiller
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Dec20-12, 06:54 AM
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Quote Quote by whatwhat11 View Post
A swimmer sees a parachutist hit the water and hears the impact twice, once through the water and the second time through the air, 1.0 s later. How far from the swimmer did the impact occur?
Vs air = 340 m/s Vs water = 1400 m/s the answer is 450m

I don't understand what to do
This is a straightforward rate x time = distance (r t = d) problem.

Let d = distance from swimmer to splash point.

In terms of d, how much time does the sound take to get from the splash point to the swimmer in air?

In terms of d, how much time does the sound take to get from the splash point to the swimmer in water?

In terms of d, what is the difference between these two times?

(Actually, the answer is not 450m, it's only 449m, but who's counting?)
whatwhat11
#3
Dec20-12, 08:26 AM
P: 14
Quote Quote by Chestermiller View Post
This is a straightforward rate x time = distance (r t = d) problem.

Let d = distance from swimmer to splash point.

In terms of d, how much time does the sound take to get from the splash point to the swimmer in air?

In terms of d, how much time does the sound take to get from the splash point to the swimmer in water?

In terms of d, what is the difference between these two times?

(Actually, the answer is not 450m, it's only 449m, but who's counting?)
Vsound in air= (340)(2)
=680m

V sound in water = (1400)(1)
=1400

1400-680
doesn't equal 450m or 459m

Chestermiller
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Dec20-12, 01:26 PM
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Quick speed of sound question?

Quote Quote by whatwhat11 View Post
Vsound in air= (340)(2)
=680m

V sound in water = (1400)(1)
=1400

1400-680
doesn't equal 450m or 459m
Hu???

The answer to my first question was: the amount of time it takes for the sound to travel through the air from the splash to the swimmer is d/340 seconds

The answer to my second question was: the amount of time it takes for the sound to travel through the water from the splash to the swimmer is d/1400 seconds

The answer to my third question was: the difference between these two times is (d/340) - (d/1400) =1 second

Are you able to solve this equation for the distance d? If so, what do you get for d?


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