Ch. 11 and 12 Review questions
The greatest obstacle to learning anything is thinking you already know everything.
1. If a force of 52 N stretches a spring 0.36 m, what is the spring constant?
Ans: 140 N/m
2. How much displacement will a coil spring with a spring constant of 110 N/m achieve if it
is stretched by a 70 N force?
Ans: 0.6 m
3. A mass on a spring that has been compressed 0.29 m has a restoring force of 82 N. What
is the spring constant?
Ans: 280 N/m
4. An amusement park ride has a frequency of 0.064 Hz. What is the ride’s period?
Ans: 16s
5. An amusement park ride swings back and forth once every 19.2 s. What is the ride’s
frequency?
Ans: 0.0521 hz
6. A mass on a spring vibrates in simple harmonic motion at an amplitude of 8.0 cm. If the
mass of the object is 0.65 kg and the spring constant is 120 N/m, what is the frequency?
Ans: 2.1 hz
7. What is the period of a 6.93 m long pendulum with a bob of mass 68.0 kg? Assume the
acceleration due to gravity is 9.81 m/s^2.
Ans: 5.28 s
8. A student wishes to construct a mass-spring system that will oscillate with the same
frequency as a swinging pendulum with a period of 3.99 s. The student has a spring with
a spring constant of 77.1 N/m. What mass should the student use to construct the massspring system?
Ans: 31.1 kg
9. A pendulum with a length of 0.600 m has a period of 1.55 s. What is the acceleration due
to gravity at the pendulum’s location?
Ans: 9.86 m/s^2
10. How long must a pendulum be to have a period of 4.7 seconds?
Ans: 5.5m
11. The largest meteorite of lunar origin reportedly had a mass of 19 g. If the meteorite
placed on a scale whose spring constant is 83 N/m, what is the compression of the
spring?
Ans: 2.25 x 10-3 m
12. In the 1950s, 187 kg of rain fell in less than 24 hours on the island of Reunion in the
Indian ocean. If this rain fell on a square meter platform supported by a spring with a
constant of 1.53 x 104 N/m, how much would it compress the spring?
Ans: 0.120 m
13. Male Siberian tigers average a mass of 389 kg, making them the largest member of the
cat family. The smallest cat, from India has an average mass of 1.5 kg. If the smallest
cat is placed on a spring scale and causes it to compress 1.2mm, how far would the same
scale compress if the Siberian tiger was placed on it?
Ans: 0.31 m
14. A crazy bungee jumper decides to jump off of a 533 m tall building using a cord that is
178m. When a test mass of 70.0 kg is used, the cord stretches to a length that is double
its initial length. What is the spring constant of the cord?
Ans: 3.86 N/m
15. The largest ruby in the world has a volume of 575 cm^3. If the ruby is attached to a
spring scale with a spring constant of 200. N/m and the spring stretches 15.8 cm, what is
the weight of the jewel? What is the mass of the jewel?
Ans: 31.6 N, 3.22 kg.
16. The shortest venomous snake, a dwarf adder, has an average length of 20.0 cm. Suppose
this snake is hanging by its tail and has just caught a large prey that it is holding in its
mouth, which causes it to sway like a pendulum with a length of 15.0cm. What is the
time it takes to complete one oscillation?
Ans: 0.777 s
17. A simple pendulum has a frequency of 0.064 hz, what is the length of this pendulum?
Ans: 61 m
18. A pendulum completes 48 oscillations in 1.00 hours. What is its length?
Ans: 1.4 x 10^3 m
19. Ganymede, the largest of Jupiter’s moons, is the largest satellite in the solar system. If a
pendulum with a length of 1.00 m completes an oscillation in 10.5 s, what is the
acceleration due to gravity on the surface of Ganymede?
Ans: 0.358 m/s2
20. If a mass of 20.0 kg oscillates on a spring 42.7 times per minute, what is the spring
constant of the spring?
Ans: 400. N/m
21. A 2662 kg giant seal is placed on a giant scale and sets it into simple harmonic motion
with an amplitude of 20.0 cm. What is the period of the scale?
Ans:0.897 s
22. A 10.2 kg baby is placed in a bouncy chair that has a spring constant of 260. N/m. If the
bouncy chair is set in simple harmonic motion, what is its period?
Ans: 1.24 s
23. Waves propagate along a stretched string at a speed of 6.9 m/s. The end of the string
vibrates up and down once every 3.6 s. What is the wavelength of the waves traveling
along the string?
Ans: 25m
24. A musical tone sounded on a piano has a frequency of 215.1 Hz and a wavelength of 1.47
m. What is the speed of the sound wave?
Ans: 316 m/s
25. Radio waves from an FM station have a frequency of 95.9 MHz. If the waves travel with
a speed of 3.00 x 10^8 m/s, what is the wavelength?
Ans: 3.13 m
26. If the intensity of a sound is 5.2 x 10^-4 W/m^2 at a distance of 7.3 m, what is the power
of the sound?
Ans: 0.35W
27. The noise of a certain lawn mower has a power of 0.26 W. At what distance will the
intensity of the lawn mower’s sound be 7.2 x 10^-4 W/m^2?
Ans: 5.4 m
28. The speed of sound in sea water is 1530 m/s. If a sound wave has a frequency of 250.
Hz, what is its wavelength?
Ans: 6.12 m
29. Cicadas produce a sound that has a frequency of 123 hz. What is the wavelength of this
sound in the air if the speed of sound is 334 m/s?
Ans: 2.72 m
30. The average human can detect frequencies with an amplitude as low as 0.000020 m. If a
sound wave has a wavelength that is one thousand times greater than this, and the speed
of sound is 334 m/s, what is its frequency?
Ans: 17000 hz
31. A small room is only 2.54 m wide, about eight and a half feet. What frequency would
produce a wave with a wavelength equal to the room if the speed of sound is 334 m/s?
Ans: 131 hz
32. The lowest vocal note in the classical repertoire is a low D, with a frequency of 73.4 hz,
which occurs in an aria in Mozart’s opera Die Entfuhrung aus dem Serail. If the
wavelength of this note is 4.50 m, what is the speed of sound?
Ans: 330 m/s
33. The highest pitch a sensitive human ear can hear is 20khz. Dolphins on the other hand,
can hear as high as 280 khz. What is the speed of sound in water if a frequency of 2.80 x
10^5 hz has a wavelength of 0.510 cm? How long would it take for this sound the travel
to another dolphin 3.00 km away?
Ans: 1.43 x 10^3 m/s, 2.10 s
34. Blue whales are the loudest creatures, emitting sound waves with an intensity of 3.0 x
10^-3 W/m^2. If this intensity is measure 4.0 m from its source, what power is
associated with the sound wave?
Ans: 0.60 W
35. Some whistling sounds can be detected as far as 8.0 km away. If the intensity at the
threshold of hearing is 1.0 x 10^-12 W/m^2, how much power did the whistle have?
Ans: 8.0 x 10^-4 W
36. Estimate how far away a cicada can be heard is the lowest audible intensity of the sound
it produces is 1.0 x 10^-12 W/m^2 and the power of the source is 2.0 x 10^-6 W.
Ans: 4.0 x 10^2 m
37. Howler monkeys can emit a sound that can be heard by a human several miles away. If
the power of the wave is 3.0 x 10^-4 W, and the minimum threshold of hearing at this
frequency is 1.1 x 10^-13 W/m^2, how far away can you hear a howler monkey?
Ans: 1.5 x 10^4 m
38. The loudest whistle was recorded in 1983 with a power of 1.0 x 10^-4 W. What is the
intensity of this sound at 2.5 m?
Ans: 1.3 x 10^-6 W/m^2
39. If 360 graduating students scream at a graduation ceremony each producing a wave with
an intensity level of 2.5 x 10^-6 W/m^2 at a distance of 2.5m, what is the power
associated with the graduating class’ scream?
Ans: 0.071 W
40. Electromagnetic waves travel at 3.0 x 10^8 m/s. The visible range of light has
wavelengths ranging from about 4.0 x 10^-7 m in the violet region to about 7.6 x 10^-7 m
in the red region. What is the frequency range?
Ans: 7.5 x 10^14 hz to 3.9 x 10^14 hz
41. How much mass is needed to stretch a spring 0.25 m when its elastic constant is 95 N/m?
Ans: 2.4 kg
42. An alphorn was made in Idaho in 1989. This instrument behaves like a closed tube pipe.
If the frequency of the fifteenth harmonic is 26.7 hz, how long is the alphorn? The speed
of sound in air is 334 m/s.
Ans: 46.9 m
43. An 86 m flagpole develops a standing wave with the 19th harmonic with the flag pole
acting as an open tube. If the speed of sound is 334 m/s, what is the frequency?
Ans: 37 hz
44. A power plan chimney is 350. m high. A standing wave with a frequency of 35.5 hz is
generated in this open pipe. If the harmonic that produces this wave is the 75th, what is
the speed of sound?
Ans: 331 m/s
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45. If a short pipe of 4.7 mm is closed at one end, what is the number of harmonics that can
be created by an ultrasound with a wavelength of 3.76 mm?
Ans: 5
46. A 36.9 cm pendulum has a period of 1.22 s. What is the acceleration due to gravity at its
location?
Ans: 9.78 m/s^2
47. If the acceleration due to gravity is 1.63 m/s^2 on the moon, how long must a pendulum
be that have a period of 2.0 s?
Ans: 0.16 m
48. On an unknown planet, a 0.75 m pendulum has a period of 1.8s, what is the acceleration
due to gravity?
Ans: 9.1 m/s^2
49. A sound wave produced by a clock is heard 515 m away 1.50 s later. What is the speed
of sound of the clock’s chime?
50. If the clock has a frequency of 436 hz, what is the period and wavelength of the sound
wave?
Ans: 343 m/s, 0.00229 s, 0.787 m
51. A transverse wave travels along a string at 15.0 m/s. If it has a frequency of 6.00 hz,
what is its wavelength?
Ans: 2.50 m
52. The Sears Tower in Chicago sways back and forth in the wind with a frequency of
0.12hz, what is its period?
Ans: 8.3 s
53. Water waves in a small pond are 6.0 cm long from crest to crest. At one point, the water
moves up and down 4.8 times per second. What is the period of the waves, what is the
speed of the waves?
Ans: 0.29 m/s, 0.21 s
54. Water waves in a lake travel 3.4 m in 1.8 s. The period of oscillation is 1.1 s. What is
the speed and wavelength of the waves
Ans: 1.9 m/s, 2.1 m
55. A sound wave of wavelength of 0.60 m and a velocity of 330 m/s is produced for 0.50 s.
What is the frequency of the wave?
56. How many complete waves are emitted in this time interval?
57. After 0.50 s, how far is the front of the wave from the source of sound?
Ans: 550 hz, 280 waves, 160 m
58. On a piano, middle C has a frequency of 262 hz, what is the second harmonic of this
note?
59. If this piano wire is 66.0 cm long, what is the velocity of sound on the string?
Ans: 524 hz. 346 m/s
60. A piano tuner using a 392 hz tuning fork hears four beats per second. What two
frequencies are possible for this?
Ans: 388 hz and 396 hz
61. What is the fundamental frequency of a 0.20 m long organ pipe that is closed at one end
when the speed of sound in the pipe is 352 m/s?
62. What is the fifth harmonic of this pipe?
Ans: 440 hz, 2200 hz
63. Violin string that is 50.0 cm long has a third harmonic frequency of 1320 hz. What is the
speed of sound on the string?
Ans: 440 m/s