B - Lakeside School

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1) Jimmy and Jenny are floating on a quiet river using giant doughnutshaped tubes. At one point, they are 5.0 m apart when a speed boat
passes. After the boat passes, they begin bobbing up and down at a
frequency of 0.25 Hz. Just as Jenny reaches her highest level, Jimmy
is at his lowest level. As it happens, Jenny and Jimmy are always
within one wavelength. What is the speed of these waves?
a) 1.3 m/s
b) 2.5 m/s
c) 3.8 m/s
d) 5.0 m/s
e) 7.5 m/s
2) A sound wave is being emitted from a speaker with a frequency f
and an amplitude A. The sound waves travel at a constant speed
of 343 m/s in air. Which one of the following actions would
reduce the wavelength of the sound waves to one half of their
initial value?
a) increase the frequency to 2f
b) increase the amplitude to 2A
c) decrease the frequency to f /4
d) decrease the frequency to f /2
e) decrease the amplitude to A /2
3) A particle of dust is floating in the air approximately one half meter in front of a
speaker. The speaker is then turned on and produces a constant pure tone as
shown. The sound waves produced by the speaker travel horizontally. Which one
of the following statements correctly describes the subsequent motion of the dust
particle, if any?
a) The particle of dust will oscillate left and right with a frequency of 226 Hz.
b) The particle of dust will oscillate up and down with a frequency of 226 Hz.
c) The particle of dust will be accelerated toward the right and continue moving in that
direction.
d) The particle of dust will move toward the right at a constant velocity.
e) The dust particle will remain motionless as it cannot be affected by sound waves.
4) In a classroom demonstration, a physics professor breathes in a small amount of
helium and begins to talk. The result is that the professor’s normally low, baritone
voice sounds quite high pitched. Which one of the following statements best
describes this phenomena?
a) The presence of helium changes the speed of sound in the air in the room, causing
all sounds to have higher frequencies.
b) The professor played a trick on the class by tightening his vocal cords to produce
higher frequencies in his throat and mouth than normal. The helium was only a
distraction and had nothing to do with it.
c) The helium significantly alters the vocal chords causing the wavelength of the
sounds generated to decrease and thus the frequencies increase.
d) The wavelength of the sound generated in the professor’s throat and mouth is only
changed slightly, but since the speed of sound in helium is approximately 2.5 times
larger than in air, the frequencies generated are about 2.5 times higher.
5) Natalie is a distance d in front of a speaker emitting sound waves.
She then moves to a position that is a distance 2d in front of the
speaker. By what factor does the sound intensity change?
a) 4
b) 2
c) 1/2
d) 1/4
e) The sound intensity remains constant because it is not dependent
on the distance.
6) Software is used to amplify a digital sound file on a computer by
20 dB. By what factor has the intensity of the sound been
increased as compared to the original sound file?
a) 2
b) 5
c) 10
d) 20
e) 100
7) Two waves are traveling along a string. The graph shows the position of
the waves at time t = 0.0 s. One wave with a maximum amplitude of 0.5
cm is traveling toward the right at 0.5 cm/s. The second wave with a
maximum amplitude of 2.0 cm is traveling toward the left at 1.5 cm/s.
At what elapsed time will the two waves completely overlap and what
will the maximum amplitude be at that time?
a) 2.0 s, 1.5 cm
b) 2.0 s, 2.5 cm
c) 1.0 s, 1.5 cm
d) 1.0 s, 2.5 cm
e) 2.0 s, 0.0 cm
8) Two identical speakers are emitting a constant tone that has a
wavelength of 0.50 m. Speaker A is located to the left of speaker
B. At which of the following locations would complete destructive
interference occur?
a) 2.15 m from speaker A and 3.00 m from speaker B
b) 3.75 m from speaker A and 2.50 m from speaker B
c) 2.50 m from speaker A and 1.00 m from speaker B
d) 1.35 m from speaker A and 3.75 m from speaker B
e) 2.00 m from speaker A and 3.00 m from speaker B
9) Consider the situation shown below. You are walking north on a
street approaching a small marching band that is traveling west to
east. The large, shaded rectangles in the drawing represent tall
buildings. At the moment shown, which instrument(s) do you hear
first?
a) flute (f)
b) snare drum (sd)
c) bass drum (bd)
d) flute (f) and
snare drum (sd)
10) Two waves, A and B, are superposed. For which one of the
following circumstances will beats result?
a) A and B are identical waves traveling in the same direction.
b) A and B are traveling with differing speeds.
c) A and B are identical waves traveling in the opposite directions.
d) A and B are waves with slightly differing frequencies, but
otherwise identical.
e) A and B are waves with slightly differing amplitudes, but otherwise
identical.
11) Which of the graphs shown represents the superposition of two
different waves with the smallest difference in frequency between
the two waves?
a) A
b) B
c) both A and B, since
the frequency difference
is the same in the two cases
d) This cannot be answered
since no frequency information is available.
12) A rope of length L is clamped at both ends. Which one of the
following is not a possible wavelength for standing waves on this
rope?
a) L/2
b) 2L/3
c) L
d) 2L
e) 4L
13) Consider a wire under tension that is driven by an oscillator. Initially, the wire
is vibrating in its second harmonic mode. How does the oscillation of the wire
change as the frequency is slowly increased?
a) No standing wave may be observed until the frequency matches the third
harmonic mode of the wire.
b) No standing wave may be observed until the frequency matches the first
harmonic mode of the wire.
c) The observed oscillation of the wire not change until the frequency matches the
third harmonic mode of the wire.
d) The observed oscillation of the wire will slowly change in fractions of the
harmonic between the second and third harmonic modes.
e) The observed oscillation of the wire will slowly change in fractions of the
harmonic between the second and first harmonic modes.
14) Which one of the following statements explains why a piano and
a guitar playing the same musical note sound different?
a) The fundamental frequency is different for each instrument.
b) The two instruments have the same fundamental frequency, but
different harmonic frequencies.
c) The two instruments have the same harmonic frequencies, but
different fundamental frequencies.
d) The two instruments have the same fundamental frequency and the
same harmonic frequencies, but the amounts of each of the
harmonics is different for the two instruments.
15) A soft drink bottle is 15 cm tall. Joey blows across that top of
the bottle just after drinking the last of his drink. What is the
approximate fundamental frequency of the tone that Joey
generates?
a) 230 Hz
b) 570 Hz
c) 680 Hz
d) 810 Hz
e) 1100 Hz
16) Given that the first three resonant frequencies of an organ pipe
are 200, 600, and 1000 Hz, what can you conclude about the
pipe? Find the answer to two sf.
a) The pipe is open at both ends and has a length of 0.86 m.
b) The pipe is closed at one end and has a length of 0.86 m.
c) The pipe is closed at one end and has a length of 0.43 m.
d) The pipe is open at both ends and has a length of 0.43 m.
e) It is not possible to have a pipe with this combination of
resonant frequencies.
17) A train moving at a constant speed is passing a stationary
observer on a platform. On one of the train cars, a flute player
is continually playing the note known as concert A (f = 440
Hz). After the flute has passed, the observer hears the sound
with a frequency of 415 Hz. What is the speed of the train?
The speed of sound in air is 343 m/s.
a) 7.3 m/s
b) 12 m/s
c) 21 m/s
d) 37 m/s
e) 42 m/s
18) Water waves approach an aperture. The resulting patterns are shown for two
different cases, A and B, in which the wavelength and aperture size are varied.
Which one of the following statements concerning these cases is true?
a) Neither figure shows diffraction. In both cases, the wavelength is much
smaller than the aperture.
b) Diffraction occurs in A, but not in B because the wavelength in A is much
smaller than the aperture.
c) Diffraction occurs in B, but not in A because the wavelength in B is much
smaller than the aperture.
d) Both figures show diffraction. In both cases, the wavelengths are
approximately the same size as the aperture.
e) Diffraction occurs in B, but not in A because the wavelength in B is
approximately the same size as the aperture.
19) A guitar string produces 4 beats/s when sounded with a 250 Hz
tuning fork and 9 beats per second when sounded with a 255 Hz
tuning fork. What is the vibrational frequency of the string?
A) 240 Hz
B) 246 Hz
C) 254 Hz
D) 259 Hz
E) 263 Hz
20) A 6.00-m long string sustains a three-loop standing wave pattern
as shown. The wave speed is 2.00 × 102 m/s.
What is the frequency of vibration?
a) 25.0 Hz
b) 33.0 Hz
c) 50.0 Hz
d) 75.0 Hz
e) 1.00 × 102 Hz
21) A string with a length of 3.0 m has two adjacent
resonances at frequencies 112 Hz and 140 Hz.
Determine the fundamental frequency of the string.
a) 14 Hz
b) 28 Hz
c) 42 Hz
d) 56 Hz
e) 70 Hz
22) The figures show standing waves of sound in six organ pipes of the same
length. Each pipe has one end open and the other end closed. Note: some of the
figures show situations that are not possible. #4 has been blocked out.
Which of the figures do not illustrate possible resonant
situations?
a) 2 and 3
b) 1, 2 and 3
c) 3 and 6
d) 5 and 6
e) 2, 3 and 6
23) As a water wave moves from deep water to shallow water,
a) the speed remains constant, the wavelength increases and the
frequency decreases.
b) the frequency remains constant, the wavelength increases and the
speed decreases.
c) the frequency remains constant, the wavelength decreases and the
speed decreases.
d) the wavelength remains constant, the speed decreases and the
frequency decreases.
e) One cannot tell from the given information.

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