khounvivongsy (sk27799) – Practice Problems 3 – Weathers – (17104)
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001
10.0 points
Two harmonic waves are described by
y
1
=
A
sin(
k x

ω t
)
,
y
2
=
A
sin(
k x
+
ω t
)
,
where
A
= 6
.
7 mm,
k
= 4
.
9 rad
/
m and
ω
=
3100 rad
/
s.
What is the amplitude
y
max
(
x
) of the resul
tant wave at
x
= 1
.
52 m?
Answer in units of mm.
002
10.0 points
Two harmonic waves are described by
y
1
=
A
sin(3
x

5
t
)
,
y
2
=
A
sin(3
x

5
t

4)
.
A
= 11 m, with
x
and
t
being given in SI units
and the phase angles in radians.
What is the displacement of the sum of
these two harmonic waves,
y
1
+
y
2
, at
x
= 1 m,
t
= 1 s?
Answer in units of m.
003
10.0 points
Two identical harmonic waves with wave
lengths of 3
.
2 m travel in the same direction
at a speed of 3
.
5 m
/
s. The second wave origi
nates from the same point as the first, but at
a later time.
Determine the minimum possible time in
terval between the starting moments of the
two waves if the amplitude of the resultant
wave is the same as that of the two initial
waves.
Answer in units of s.
004
(part 1 of 2) 10.0 points
The acoustical system shown in the figure is
driven by speaker emitting a 392 Hz note.
The speed of sound is 345 m
/
s.
S
Speaker
Receiver
r
1
r
2
If destructive interference occurs at a par
ticular instant, by what minimum amount
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 Spring '09
 weathers
 mechanics, harmonic waves

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