Version PREVIEW – HW 2 – Savrasov – (39824)
1
This printout should have 10 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
Echo From a Distant Wall
001
10.0 points
Karen claps her hand and hears the echo From
a distant wall 0
.
646 s later.
How Far away is the wall? The speed oF
sound in air is 343 m
/
s.
Correct answer: 110
.
789 m.
Explanation:
Let :
v
= 343 m
/
s
,
and
t
= 0
.
646 s
.
Karen hears the sound aFter it had traveled
to the wall and back, so
2
d
=
v t
d
=
v t
2
=
(343 m
/
s) (0
.
646 s)
2
=
110
.
789 m
.
Pressure Amplitude 02
002
10.0 points
Calculate the pressure amplitude oF a
1
.
02 kHz sound wave in air iF the displace
ment amplitude is 2
.
69
×
10

8
m. Take the
velocity oF sound in air to be 343 m
/
s and the
density oF air to be 1
.
22 kg
/
m
3
.
Correct answer: 0
.
0721417 Pa.
Explanation:
Let :
f
= 1
.
02 kHz
,
A
= 2
.
69
×
10

8
m
,
v
s
= 343 m
/
s
,
and
ρ
= 1
.
22 kg
/
m
3
.
The pressure amplitude is
Δ
P
=
ρ ω v
s
A
=
ρ
(2
π f
)
v
s
A
= (1
.
22 kg
/
m
3
) 2
π
(1
.
02 kHz)
×
(343 m
/
s) (2
.
69
×
10

8
m)
=
0
.
0721417 Pa
.
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 Spring '08
 curtise
 Hertz, Wavelength, Correct Answer, Sonar

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