1. A sound is directed along the normal towards a vertical wall. As a person walks towards the
wall along the normal, it can be observed that the sound intensity decreases to a minimum every
50 cm. If the air temperature is 20oC what is the frequency of the sound?
2. A tone generator sends sound waves of frequency 400 Hz towards a wall which is located
10.0 m away. For the air temperature present, the speed of sound is 340 m/s. If a person
walks towards the wall, she would be able to notice that the sound will reach a maximum at a
series of locations. How far apart are these locations?
3. Explain what you would hear if you simultaneously sound two tuning forks with frequencies of
300 Hz and 302 Hz.
4. When a person walks into a room, they hear two tuning forks being sounded simultaneously.
One of the forks produces a sound of frequency 256 Hz. There are 25 beats produced in 5 s
from the pair of tuning forks. Find the possible frequencies for the second tuning fork.
5. A 300 Hz tuning fork produces three beats per second with a second tuning fork. Calculate
the possible frequencies of the second fork.
6. A small weight, which lowers the pitch, is added to one tine of the second tuning fork
mentioned in the previous question. As a result of the added weight, the number of beats per
second decreases to one. Determine what the frequency of the unknown fork was before
adding the weight. Also, calculate the possible new frequencies of the fork with the weight
added.
7. A 384 Hz tuning fork produces five beats per second with a second fork when a small clamp is
placed on it. Without the clamp, the beat frequency is 7 Hz. What is the frequency of the
second fork?
8. The frequency of a vibrating string is 256 Hz when the tension is 150 N. If the tension is
doubled, what is the new frequency of the string?
9. The diameters of two strings of equal length, composition, and under the same tension are,
0.80 mm and 1.0 mm. The frequency of vibration of the 0.80 mm diameter string is 200 Hz.
What is the vibrational frequency of the second string?
10. A string of length 1.0 m vibrates at a frequency of 180 Hz. If the length is shortened to 50 cm,
what is the new frequency? Determine the frequency if the new length was 60 cm.
11. A 200 Hz sound is produced by a string under a tension of 100 N. What is the new frequency
if the tension is changed to 900 N? to 25 N?
12. The "A" string on a violin is 25.4 cm long. When sounded, it produces a 440 Hz sound. If a
sound of frequency 523.3 Hz is desired, how long must the string be?
13. A vibrating string produces a frequency of 320 Hz. The string's length and diameter are 50 cm
and 0.50 mm. Determine the frequency of a vibrating string of double the length and half the
diameter. Assume that they are made of the same material, and under the same tension.
14. Determine the frequency of the second overtone of a vibrating string with a fundamental
frequency of 400 Hz.
15. The fundamental frequencies of two vibrating strings are 280 Hz and 282 Hz. Calculate the
beat frequency produced by the first overtones of the two strings.
16. Explain how resonance can be used to free a car stuck in mud.
17. Is it really possible for singers to shatter wine glasses? Explain your answer.
18. Why does the frequency of the sound produced when filling a "pop" bottle with water rise.
19. The length of a closed pipe can be changed by a sliding mechanism. As a result, resonance
can be caused at several different lengths of the pipe by using a tuning fork. Suppose the
tuning fork used produces a frequency of 320 Hz. If the difference between the length of the
closed pipe for first resonance and second resonance is 54.0 cm, calculate the wavelength and
speed of the sound waves?
20. The air temperature is 20o C. The length of a closed air column is 60.0 cm. What are the
frequencies of the tuning forks that will cause resonance at the first, second, and third
resonant length.
21. The speed of sound is 347 m/s. Determine the wavelength and frequency of the wave that
produces resonance at the shortest resonant length in a closed tube of length 30.0 cm.
22. What is the length of an open air column which is resonating at its first resonant length with a
sound of frequency 560 Hz? Assume the speed of sound is 350 m/s.
23. Pipe organs sometimes use pipes which are open at both ends. Such a pipe might be 1.23 m
in length. Determine the fundamental frequency of such a pipe if the speed of sound is 340 m/s.
24. The air temperature is 13.33o C. A horn on a car produces a sound of frequency of 500 Hz.
The car is traveling towards a meter which measures the frequency as 520 Hz. Find the speed
of the car.
25. The observed frequency of a sound is 3% higher that the actual frequency. Calculate the
speed of the source.
November 22, 2013