chapter 19 and 20 quiz
How does the V shape of a bow wave depend on the speed of the source?
The angle of the V gets smaller as the speed of the source gets faster.
Which is normally greater, the energy in ordinary sound or the energy in ordinary light? How does the speed of sound compare to the speed of light?
The energy in ordinary light is greater than the energy in ordinary sound. The speed of sound is a million times less than the speed of light.
A car of mass m drives over a speed bump and oscillates in simple harmonic motion with a frequency f. What would happen to the car's oscillation frequency if its suspension springs were replaced with stiffer springs such that the spring constant was doubled?
The frequency would be 2√ times larger
When you listen to a radio, why do you hear only one station at a time rather than all stations at once?
The natural frequency of the electronics is tuned to resonate with the frequency of one station
How did wind-generated resonance affect the Tacoma Narrows Bridge in the state of Washington in 1940?
The resonant amplification of bridge motion destroyed the bridge.
A cat can hear sound frequencies up to 70,000 Hz. Bats send and receive ultra-high-frequency squeaks up to 120,000 Hz. Which hears sound of shorter wavelengths, cats or bats?
The shorter wavelengths are heard by bats.
What is the result of a mirror image of a sound signal combining with the sound itself?
The sound is cancelled when added to its mirror image.
Why will a struck tuning fork sound louder when it is held against a table?
The table is forced to vibrate, and its large surface vibrates more air than the tuning fork.
What is meant by the period of a pendulum?
The time interval of a to-and-fro swing
The wavelength of a transverse wave is the distance between successive crests (or troughs). What is the wavelength of a longitudinal wave?
The wavelength is the distance between successive maximum compressions (or rarefractions).
Do compressions and rarefactions travel in the same direction, or in opposite directions, in a wave.
They travel in the same direction at the same speed.
When is it possible for one wave to cancel another?
When both waves have the same amplitude and when the crest of one wave overlaps the trough of another
How do forced vibrations relate to resonance?
When forced vibrations match an object's natural frequency, resonant amplification occurs.
What is meant by the superposition principle?
When two or more waves occupy the same space, wave displacements add at every point.
What is a wiggle in time called? What do you call a wiggle in space and time?
a vibration, a wave
The speed of sound in air varies with _________.
air temperature
Interference is a phenomenon that occurs primarily in ________
all kinds of waves
What kind of waves can exhibit interference?
all kinds of waves
The vibrations along a longitudinal wave move in a direction _________.
along and parallel to the wave
When a car drives over a speed bump and oscillates up and down in simple harmonic motion, at which position during the motion is the acceleration of the car the greatest?
at the maximum amplitude, x = A
Can standing waves be formed with transverse waves or longitudinal waves?
both
Can the Doppler effect be observed with longitudinal waves or with transverse waves?
both
Rank the speed of sound through the following from greatest to least: A. Helium B. Benzene C. Mercury
c,b,a
Sound travels from one place to another mainly in a series of _________.
compressions and refractions
In one word, what is it that moves from source to receiver in wave motion?
disturbance
Does sound tend to bend upward or downward when its speed is less near the ground?
downwards
Which two factors determine the natural frequency of an object?
elasticity and shape
What travels in a wave from one location to another is _________.
energy
A shock wave occurs when an aircraft travels _________.
faster then the speed of sound
The pitch of sound is most closely related to _________.
frequency
When a sound source approaches a stationary listener, the listener experiences an increase in sound _________.
frequency
The natural frequency of a small bell is _________.
higher than for a larger bell
A railroad locomotive is at rest with its whistle shrieking, then starts moving toward you. Does the frequency of sound that you hear increase, decrease, or stay the same? How about the wavelength reaching your ear?
increase, decrease
If a pendulum is shortened, does its frequency increase or decrease? What about its period?
increase, decrease
Are beats the result of interference or of the Doppler effect, or of both?
interference
Standing waves are produced by _________.
interference
The phenomenon of beats is most closely related to _________.
interference
What ultimately happens to the energy of sound in the air?
it becomes thermal energy
Compared with the speed of a boat moving across the surface of water, the speed of the bow produced is _________.
less
Resonance occurs when forced vibration _________.
matches natural frequency
A reverberation occurs when sound undergoes _________.
multiple echo's
Does the medium in which a wave travels move with the wave?
no
Does the period of a pendulum depend on the mass of the bob? On the length of the string?
no, yes
In the Doppler effect, does frequency change? Does wave speed change?
only frequency changes
The vibrations along a transverse wave move in a direction _________.
perpendicular to the wave
Interference is a property of _________.
sound light and water waves
Forced vibrations mainly occur in _________.
sounding boards
Refraction of sound occurs with changes in wave _________.
speed
Suppose a piano tuner hears 3 beats per second when listening to the combined sound from a tuning fork and the piano wire being tuned. After slightly tightening the string, 5 beats per second are heard. Should the string be loosened or tightened?
the piano string should be loosened
What is the source of all waves?
the source is something that is vibrating
The speed of a wave can be found by multiplying its frequency by its _________.
wavelength
If the frequency of a particular wave is 20 Hz, its period is _________.
1/20 second
How many vibrations per second are represented in a radio wave of 101.7 MHz?
101,700,000 vibrations
A mass attached to a spring is displaced from its equilibrium position by 5cm and released. The system then oscillates in simple harmonic motion with a period of 1s . If that same mass-spring system is displaced from equilibrium by 10cm instead, what will its period be in this case?
1s
A rope with a mass density of 1 kg/m has one end tied to a vertical support. You hold the other end so that the rope is horizontal and has a tension of 4 N. If you move the end of the rope back and forth, you produce a transverse wave in the rope with a wave speed of 2 m/s. If you double the amount of tension you exert on the rope, what is the wave speed?
2.8 m/s
What is the average range of a young person's hearing?
20 to 20,000 hertz
A rope has one end tied to a vertical support. You hold the other end so that the rope is horizontal. If you move the end of the rope back and forth with a frequency of 4 Hz, the transverse wave you produce has a wavelength of 0.5 m. What is the speed of the wave in the rope?
2m/s
How many nodes, not including the endpoints, are there in a standing wave that is two wavelengths long? Three wavelengths long?
3, 5
What is the speed of sound in dry air at 20°C?
340 m/s
What beat frequency will occur when a 370-Hz and a 374-Hz sound source are sounded together?
4 Hz
How does a radio wave differ from a sound wave?
A radio wave is an electromagnetic wave that travels at the speed of light, whereas a sound wave travels at the speed of sound through air or another elastic medium.
A bow wave on the surface of water is two-dimensional. What about a shock wave in air?
A shock wave in air is three-dimensional
How does a sine curve describe a wave?
A sine curve is a pictorial representation of a wave.
What kinds of waves can show interference?
All waves show inference
What is meant by a blue shift and a red shift for light?
An approaching source has increased light frequency - a blue shift. A receding source has a decreasing frequency - a red shift.
How fast does a supersonic aircraft fly compared with the speed of sound?
As fast as or faster than the speed of sound
How fast must a bug swim to keep up with the waves it produces? How fast must it move to produce a bow wave
As fast as the wave speed; as fast as or faster than the wave speed
In what direction are the vibrations relative to the direction of wave travel in a transverse wave?
At right angles to the direction of wave travel
What physical phenomenon underlies the production of beats?
Beats are produced by interference.
Why does sound sometimes refract under water?
Changing temperature changes the speed of sound in water.
What is the cause of refraction?
Different speeds of sound in a medium
True or false: In order for an object to produce a sonic boom, it must be "noisy." Give two examples to support your answer.
False. A whip and a bullet move through the air without making sounds other than the shock wave
True or false: A sonic boom occurs only when an aircraft is breaking through the sound barrier. Defend your answer.
False. An aircraft creates a shock wave continuously as it is supersonic. This is heard as a sonic boom by an observer.
Does sound travel faster in warm air or in cold air? In humid air or dry air?
Faster in warm air, faster in humid air
How are frequency and period related to each other?
Frequency and period are reciprocals.
What is a node? What is an antinode?
In a standing wave, a node always has zero displacement and an antinode always has maximum displacement.
What factors does the speed of sound depend upon? What are some factors that it does not depend upon?
It depends on temperature and humidity, not on loudness and frequency.
Two pendulums have identical periods. One has a slightly larger amplitude than the other, but both swing through small angles compared to vertical. Which of the following must be true of the pendulum that has the larger amplitude?
It moves faster at the lowest point in its swing than the other one.
If astronauts built a pendulum on the Moon that was exactly the same as one on Earth, what would be different about the pendulum's motion on the Moon?
It would run slower.
You would like a pendulum that swings back and forth once every 2 seconds, but the one you have swings once every 1.9 seconds. Which of the following should you do to adjust it so that it has the desired period?
Make the pendulum slightly longer.
In what direction are the vibrations relative to the direction of wave travel in a longitudinal wave?
Parallel to the direction of wave travel
You and a friend are on a swing set and her swing is slightly longer than yours. If you both start swinging at the same time, from the same height, where will she be after you have completed one complete swing back and forth?
She will be slightly lower than you but moving upward toward you
What is ultrasound?
Sound above the frequency of human hearing
You are making a telephone out of two aluminum cans and some string. You can choose between two types of string: a 2-m length of thin cooking twine or a 2-m length of heavy rope. Which type of string should you use so that you have the fastest wave speed in your telephone?
you should use the thin cooking wire