Chapter Pretests


Chapter 13-14 Prestest
 
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Chapter 13-14 Prestest


Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 
The highness or lowness of a sound is perceived as
a.
compression.
c.
ultrasound.
b.
wavelength.
d.
pitch.
 

 2. 
The property of sound called intensity is proportional to the rate at which energy flows through
a.
an area perpendicular to the direction of propagation.
b.
an area parallel to the direction of propagation.
c.
a cylindrical tube.
d.
a sound wave of a certain frequency.
 

 3. 
At a distance of 3 m, the intensity of a sound will be ____ the intensity it was at a distance of 1 m.
a.
one-ninth
c.
3 times
b.
one-third
d.
9 times
 

 4. 
When an air column vibrates in a pipe that is open at both ends,
a.
all harmonics are present.
c.
only odd harmonics are present.
b.
no harmonics are present.
d.
only even harmonics are present.
 

 5. 
Which is not an example of approximate simple harmonic motion?
a.
A ball bouncing on the floor.
b.
A child swinging on a swing.
c.
A piano string that has been struck.
d.
A car's radio antenna as it waves back and forth.
 

 6. 
Three identical springs each have the same spring constant k. If these three springs are attached end to end forming a spring three times the length of one of the original springs, what will be the spring constant of the combination?
a.
k
b.
3 k
c.
k/3
d.
1.73 k
 

 7. 
A 0.20 kg object, attached to a spring with spring constant k = 10 N/m, is moving on a horizontal frictionless surface in simple harmonic motion of amplitude of 0.080 m. What is its speed at the instant when its displacement is 0.040 m? (Hint: Use conservation of energy.)
a.
9.8 m/s
b.
4.9 m/s
c.
49 cm/s
d.
24.5 cm/s
 

 8. 
Which one of the following quantities is at a maximum when an object in simple harmonic motion is at its maximum displacement?
a.
speed
b.
acceleration
c.
kinetic energy
d.
frequency
 

 9. 
For a mass suspended on a spring in the vertical direction, the time for one complete oscillation will depend on:
a.
the value for g (the acceleration due to gravity).
b.
the distance the mass was originally pulled down.
c.
the maximum speed of the oscillating mass.
d.
the time doesn't depend on any of the above.
 

 10. 
A mass on a spring vibrates in simple harmonic motion at a frequency of 4.0 Hz and an amplitude of 4.0 cm. If a timer is started when its displacement is a maximum (hence x = 4 cm when t = 0), what is the acceleration magnitude when t = 3 s?
a.
zero
b.
8.13 m/s2
c.
14.3 m/s2
d.
25.3 m/s2
 

 11. 
The position of a 0.64-kg mass undergoing simple harmonic motion is given by x = (0.160 m) cos (pt/16). What is the maximum net force on the mass as it oscillates?
a.
3.9 ´ 10-3 N
b.
9.9 ´ 10-3 N
c.
1.3 ´ 10-3 N
d.
6.3 N
 

 12. 
The position of a 0.64-kg mass undergoing simple harmonic motion is given by x = (0.160 m) cos (pt/16). What is its position at t = 5.0 s?
a.
0.160 m
b.
0.159 m
c.
0.113 m
d.
0.089 m
 

 13. 
For a wave on the ocean, the amplitude is:
a.
the distance between crests.
b.
the height difference between a crest and a trough.
c.
one half the height difference between a crest and a trough.
d.
how far the wave goes up on the beach.
 

 14. 
For a wave traveling in a string, by what factor would the tension need to be increased to double the wave speed?
a.
1.4
b.
2.0
c.
4.0
d.
16
 

 15. 
When an object is moving in simple harmonic motion, which of the following is at a minimum when the displacement from equilibrium is zero?
a.
the magnitude of the velocity
b.
the magnitude of the acceleration
c.
the kinetic energy
d.
the total mechanical energy
 

 16. 
Two wave pulses with equal positive amplitudes pass each other on a string. One is traveling toward the right and the other toward the left.  At the point that they occupy the same region of space at the same time
a.
constructive interference occurs.
c.
a standing wave is produced.
b.
destructive interference occurs.
d.
a traveling wave is produced.
 

 17. 
Consider a closed pipe of length L.  What are the wavelengths of the three lowest tones produced by this pipe?
a.
16L, 4L, L
b.
4L, 2L, L
c.
2L, L, L/2
d.
2L, L, 2L/3
e.
4L, 4L/3, 4L/5
 

 18. 
Two pure tones are sounded together and a particular beat frequency is heard.  What happens to the beat frequency if the frequency of one of the tones is increased?
a.
It increases.
b.
It decreases.
c.
It does not change.
d.
It becomes zero.
e.
It could either increase or decrease.
 

 19. 
A harmonic wave has a wavelength of 2.0 m and a frequency of 5.0 Hz. What is the speed of the wave?
a.
10 m/s
b.
0.40 m/s
c.
0.50 m/s
d.
0.10 m/s
e.
2.5 m/s
 

 20. 
Two steel wires are stretched with the same tension. The first wire has a diameter of 0.610 mm and the second wire has a diameter of 0.910 mm. If the speed of waves traveling along the first wire is 54.0 m/s, what is the speed of waves traveling along the second wire?
a.
24.9 m/s
b.
27.2 m/s
c.
36.2 m/s
d.
81.0 m/s
e.
100 m/s
 

 21. 
Two in-phase loudspeakers are placed along a wall and are separated by a distance of 4.00 m. They emit sound with a frequency of 514 Hz. A person is standing away from the wall, in front of one of the loudspeakers. What is the closest distance from the wall the person can stand and hear constructive interference? The speed of sound in air is 343 m/s.
a.
0.344 m
c.
1.15 m
b.
0.729 m
d.
1.64 m
 

 22. 
One of the harmonics of a string fixed at both ends has a frequency of 52.2 Hz and the next higher harmonic has a frequency of 60.9 Hz. What is the fundamental frequency of the string?
a.
26.1 Hz
b.
8.7 Hz
c.
4.35 Hz
d.
30.4 Hz
e.
17.4 Hz
 

 23. 
One of the harmonics of a column of air open at one end and closed at the other has a frequency of 448 Hz and the next higher harmonic has a frequency of 576 Hz. What is the fundamental frequency of the air column?
a.
32 Hz
b.
64 Hz
c.
88 Hz
d.
128 Hz
e.
256 Hz
 

 24. 
Two strings of identical mass per unit length are stretched with the same tension with their ends fixed, but one string is 0.33 cm longer than the other. Waves on these strings propagate at 34.0 m/s. The fundamental frequency of the shorter string is 258 Hz. What is the beat frequency when each string is vibrating at its fundamental frequency?
a.
12.3 Hz
b.
9.00 Hz
c.
12.0 Hz
d.
12.7 Hz
e.
11.3 Hz
 

 25. 
Two strings of identical mass and length are stretched with their ends fixed, but the tension in one string is 1.10 times greater than in the other. Waves on the string with the lower tension propagate at 35.2 m/s. The fundamental frequency of that string is 258 Hz. What is the beat frequency when each string is vibrating at its fundamental frequency?
a.
11.0 Hz
b.
9.00 Hz
c.
13.7 Hz
d.
12.6 Hz
e.
17.1 Hz
 

 26. 
The frequency separating audible waves and ultrasonic waves is considered to be 20 kHz. What wavelength in air at room temperature is associated with this frequency? (Assume the speed of sound to be 340 m/s.)
a.
1.7 cm
b.
5.2 cm
c.
34 cm
d.
55 cm
 

 27. 
The speed of sound in air is a function of which one of the following?
a.
wavelength
b.
frequency
c.
temperature
d.
amplitude
 

 28. 
The speed of sound at 0°C is 331 m/s. What is the speed of sound at 25°C? (0°C = 273 K)
a.
346 m/s
b.
356 m/s
c.
343 m/s
d.
350 m/s
 

 29. 
What is the intensity level of a sound with intensity of 5.0 ´ 10-10 W/m2? (I0 = 10-12 W/m2)
a.
74 dB
b.
54 dB
c.
2.7 dB
d.
27 dB
 

 30. 
What is the intensity of sound from a band with a sound level of 120 dB? (I0 = 10-12 W/m2)
a.
1 W/m2
b.
1.2 W/m2
c.
10 W/m2
d.
12 W/m2
 

 31. 
An airplane flying with a constant speed flies from a warm air mass into a cold air mass. The Mach number will:
a.
increase.
b.
decrease.
c.
stay the same.
d.
become unstable.
 

 32. 
While standing at a crosswalk, you hear a frequency of 560 Hz from an approaching police car. After the police car passes, its frequency is 480 Hz. What is the speed of the police car? (speed of sound = 340 m/s)
a.
13.1 m/s
b.
17.4 m/s
c.
21.1 m/s
d.
26.2 m/s
 

 33. 
When two sound waves are out of phase by ____, destructive interference will occur.
a.
90°
b.
270°
c.
540°
d.
720°
 

 34. 
If the tension on a guitar string is increased by a factor of 3, the fundamental frequency at which it vibrates is changed by what factor?
a.
9
b.
3
c.
mc034-1.jpg
d.
mc034-2.jpg
 

 35. 
A 100-m-long high-voltage cable is suspended between two towers. The mass of the 100-m cable is 150 kg. If the tension in the cable is 30 000 N, what is the lowest frequency at which this cable can oscillate?
a.
0.71 Hz
b.
1.0 Hz
c.
1.4 Hz
d.
2.0 Hz
 

 36. 
A 1.5-m string is held fixed at both ends. When driven by a 180-Hz source, the string vibrates in 4 distinct segments. What is the natural fundamental frequency of the string?
a.
45 Hz
b.
90 Hz
c.
240 Hz
d.
600 Hz
 

 37. 
For a standing wave in an air column in a pipe that is open at both ends, there must be at least:
a.
one node and one antinode.
b.
two nodes and one antinode.
c.
two antinodes and one node.
d.
two nodes and two antinodes.
 

 38. 
Which of the following best describes a sound level of intensity 1 W/m2?
a.
extremely loud
b.
about that of a power mower
c.
normal conversation
d.
like a whisper
 

True/False
Indicate whether the statement is true or false.
 

 39. 
Bats use infrasound to navigate.
 

 40. 
Infrasound carries over long distances better than ultrasound.
 



 
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