Quick speed of sound question?


by whatwhat11
Tags: sound, speed
whatwhat11
whatwhat11 is offline
#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
Phys.Org News Partner Science news on Phys.org
Cougars' diverse diet helped them survive the Pleistocene mass extinction
Cyber risks can cause disruption on scale of 2008 crisis, study says
Mantis shrimp stronger than airplanes
Chestermiller
Chestermiller is online now
#2
Dec20-12, 06:54 AM
Sci Advisor
HW Helper
Thanks
PF Gold
P: 4,504
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
whatwhat11 is offline
#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
Chestermiller is online now
#4
Dec20-12, 01:26 PM
Sci Advisor
HW Helper
Thanks
PF Gold
P: 4,504

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?


Register to reply

Related Discussions
Speed of sound - why does adding ethanol to water increase the speed of sound General Physics 12
Question about the Speed of Sound General Physics 4
quick question: speed of sound in seawater Introductory Physics Homework 6
Quick Sound Question Introductory Physics Homework 2
Speed of sound/light question Introductory Physics Homework 3