obaidi (aao476) – OH13 – Bradley – (191)
1
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printout
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have
22
questions.
Multiplechoice questions may continue on
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before answering.
This is Online Homework No. 13 (OH13).
It is due Thursday morning (27 Nov) at 7:00
AM (UAE time).
001
10.0 points
A harmonic wave is traveling along a rope.
The oscillator that generates the wave com
pletes 41
.
0 vibrations in 29
.
5 s. A given crest
of the wave travels 391 cm along the rope in a
time period of 10
.
8 s.
What is the wavelength?
Correct answer: 0
.
26049.
Explanation:
Let :
n
= 41
.
0 vibrations
,
t
= 29
.
5 s
,
Δ
x
= 391 cm
,
and
Δ
t
= 10
.
8 s
.
λ
=
v
f
=
Δ
x
Δ
t
n
t
=
Δ
x t
n
Δ
t
=
(391 cm)(29
.
5 s)
41 (10
.
8 s)
·
1 m
100 cm
=
0
.
26049
.
keywords:
002
(part 1 of 3) 4.0 points
A transverse wave of frequency 35 Hz propa
gates down a string. Two points 15 cm apart
are out of phase by
7
π
3
.
What is the wave length of the wave?
Correct answer: 12
.
8571 cm.
Explanation:
Let :
Δ
x
= 15 cm
and
δ
=
7
π
3
.
Let the positive
x
direction be the direction
of propagation of the wave.
The phase difference is
δ
= 2
π
Δ
x
λ
λ
= 2
π
Δ
x
δ
= 2
π
15 cm
7
π/
3
=
12
.
8571 cm
.
003
(part 2 of 3) 3.0 points
At a given point, what is the phase difference
(as a multiple of
π
) between two ‘displace
ments for times 10 ms apart?
Correct answer: 0
.
7
π
.
Explanation:
Let :
t
= 10 ms = 0
.
01 s
and
f
= 35 Hz
.
The period is
T
=
1
f
, so the phase difference
is
δ
= 2
π
t
T
= 2
π t f
= 2
π
(10 ms)
parenleftbigg
1 s
1000 ms
parenrightbigg
(35 Hz)
=
0
.
7
π
.
004
(part 3 of 3) 3.0 points
What is the wave velocity?
Correct answer: 4
.
5 m
/
s.
Explanation:
v
=
f λ
= (35 Hz) (12
.
8571 cm)
parenleftbigg
1 m
100 cm
parenrightbigg
=
4
.
5 m
/
s
.
keywords:
005
10.0 points
The figure shows two wave pulses that are
approaching each other.
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obaidi (aao476) – OH13 – Bradley – (191)
2
P
Q
Which of the following best shows the shape
of the resultant pulse when the centers of the
pulses, points
P
and
Q
, coincide?
1.
2.
3.
4.
correct
5.
Explanation:
Notice that the two pulses have the same
width and amplitude.
Choosing the the point
P
(the same as point
Q
when the two pulses coincide) as the origin,
the two pulses can be described as:
P
:
y
1
=
A
,

d
≤
x
≤
d
Q
:
y
2
=
braceleftBigg
A
,

d
≤
x <
0

A
,
0
< x < d
Using the principle of superposition, the re
sultant pulse is
y
=
y
1
+
y
2
=
braceleftbigg
2
A
,

d
≤
x <
0
0
,
0
< x < d
P
Q
P
+
Q
006
10.0 points
A 3
.
2 kg block supported by a string rests on
a frictionless incline. The length of the string
is 0
.
5 m and its mass of 1
.
6 g is much less than
3
.
2 kg.
The acceleration of gravity is 9
.
8 m
/
s
2
.
3
.
2 kg
μ
= 0
0
.
5 m
37
◦
Determine the time it takes a transverse
wave to travel from one end of the string to
the other.
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