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Practice Problems for Quiz 2
These problems are similar to those you should expect on the actual Quiz. But keep in mind that the quiz
problems will differ. This is intended to test your confidence and allow you to better determine what
areas are you most and least confident about.
1). The length of a string is doubled, the tension is reduced by a factor of 4, and the mass is reduced by
a factor of 2. How does its fundamental frequency change?
(A) decreases by a factor of 2.
(B) decreases by a factor of 2 √ 2.
(C) is unchanged.
(D) decreases by a factor of √ 2.
2). Bats can detect small objects such as insects that are of a size approximately that of one wavelength.
If bats emit a chirp at a frequency of 60 kHz, and the speed of wound in air is 330 m/s, what is the
smallest size insect they can detect:
(A) 1.5 mm
(B) 3.5 mm
(C) 5.5 mm
(D) 7.5 mm
(E) 9.5 mm
3). The Doppler shift of ultrasonic waves is used to measure the speed of blood in an artery. The velocity
of sound n the blood is 1.5 m/s. If the frequency of the stationary source is 100 Hz and the reflected
sound is Doppler shifted to a wavelength of 150 Hz, what is the speed of the blood flow?
A) 0.3 m/s
B) 0.7 m/s
C) 1.5 m/s
D) 2.2 m/s
E) 3.3 m/s
4) A standing wave is set up in a 2.0 m string fixed at both ends. The string vibrates in 5 distinct segments
when driven by a 120 Hz source. In how many of the segments will the string vibrate if the tension is
increased by a factor of 4?
A) 3
B) 10
C) 20
D) 30
E) No standing waves pattern will be observed
5) Standing waves result from the superposition of:
(A) two waves of the same frequency traveling in the same direction.
(B) two waves of similar frequencies traveling in the same direction.
(C) two waves of the same frequency traveling in opposite directions.
(D) two waves of similar frequencies traveling in opposite directions.
6). A piano tuner using a 264 Hz tuning fork hears 2 beats per second while playing the tuning fork and a
piano key at the same time. What are the two possible frequencies of vibration of the piano wire?
(A). 260 Hz and 268 Hz.
(B). 264 Hz and 268 Hz.
(C). 262 Hz and 268 Hz.
(D). 262 Hz and 266 Hz.
(E). 260 Hz and 262 Hz.
7) A tube of length 3 m is open at one end and closed at the other. What is the wavelength of the
second harmonic?
(A) 1 m
(B) 2 m
(C) 3 m
(D) 4 m
8) A loud train whistle has an acoustic power output of 100 W. If the sound energy spreads out
spherically, what is the intensity at a distance of 100 m from the train?
(A) 1.6 W/m2
(B) 1.0 x 10-1 W/m2
(C) 8.0 x 10-2 W/m2
(D) 3.2 x 10-3 W/m2
(E) 8.0 x 10-4 W/m2
9) A tuning fork is sounded above a resonating tube (one end closed), which resonates at a length of 0.2
m and again upon extension at 0.6 m. If the tube length were extended even further, at what point will
the sound from the tuning fork again resonate in the tube?
(A) 0.8 m
(B) 1.0 m
(C) 1.2 m
(D) 1.6 m
(E) 2.0 m
ANSWER KEY: A C A E C D C E B