Summary
- Sound waves
- Sound intensity
- Doppler effect
Walker4e
Reading quiz If you fill your lungs with SF6 gas, your voice sounds unnaturally low.
From this observation, we can conclude that the speed of sound in SF6 must be _____ the speed of sound
in air.
A. less than
B. greater than
C. equal to
Answer
wlk4 14.61
A pair of in-phase stereo speakers is placed side by side, 0.85 m apart. You stand directly in front of one of the
speakers, 1.1 m from the speaker. What is the lowest frequency that will produce constructive interference at your
location?
A. 220 Hz
B. 440 Hz
C. 850 Hz
D. 1.2 kHz
Answer
sj6 18.25a
What happens to the fundamental frequency of a string fixed at both ends if the length of the string is doubled? It
A. doubles.
B. stays same.
C. is cut to 1/2
D. is cut to 1/4
Answer
sj6 18.25b
What happens to the fundamental frequency of a string fixed at both ends if the mass/length is doubled? It
A. doubles.
B. stays same.
C. is cut to 1/2
D. is cut to 1/√2
Answer
sj6 18.25c
What happens to the fundamental frequency of a string fixed at both ends if the tension in the string is doubled? It
A. doubles
B. increases by √2
C. is cut to 1/2
D. is cut to 1/√2
Answer
D. A = B = C
The wave speed on a string is given by the square root of the tension
divided by the mass per length. If the tensions and masses per length are all the same, then the wave
speeds are the same.
D. 1.2 kHz
C. is cut to 1/2
D. is cut to 1/√2
B. increases by √2