Unit 9: Waves and Sound Flashcards
mass on a spring
what two things are equal to zero at equilibrium position?
spring force
mass’s acceleration
what increased as a mass moves towards the equilibrium position?
the speed of the mass increases
why does the mass begin to slow down once it passes the equilibrium position?
direction of the spring force and acceleration of mass are opposite to the mass’s direction of motion
when does the speed of the mass become zero
the mass is at maximum displacement
why does a mass spring system eventually come to rest
friction
why is a spring force sometimes called a restoring force
it always pushes or pulls the mass towards its original equilibrium position
what is the quantity k in Hooke’s Law?
F(elastic)=-kx
spring constant
stiffer spring–>greater k
simple harmonic motion
any periodic motion that is the result of a restoring force that is proportional to the displacement
what is stored in a stretched or compressed string
elastic potential energy
what happens when elastic potential energy is released
converted to kinetic energy
what two forces act on a pendulum bob at any point
force exerted by the string
gravitational force
at maximum displacement, what happens to a pendulum’s restoring force, acceleration, and speed
restoring force and acceleration are at a maximum
speed becomes zero
what happens to a pendulum’s energy when swinging towards equilibrium
gains kinetic energy
loses potential energy
amplitude
maximum displacement from equilibrium
period (T)
the time it takes for a complete cycle to occur
frequency (f)
number of cycles or vibrations per unit of time
the SI unit of frequency
hertz
Hz
mathematical relationship between frequency and period
f=1/T
what does the period of a pendulum NOT depend on
mass
amplitude
for a mass spring system, what happens to the period as the mass increases
the period increased
what does NOT affect the period of a mass spring system
amplitude
medium
physical environment through which a wave can travel
does the medium travel with the waves?
no. energy travels throughout the medium but the medium remains in place
mechanical waves
waves that require a material medium
what type of waves can travel through a vacuum
electromagnetic waves
pulse wave
wave that consists of a single traveling pulse
when is a period wave produced
the source of the wave’s motion is a periodic motion
sine wave
source vibrates with simple harmonic motion
transverse wave
particles vibrate perpendicularly to the direction the wave is traveling
highest point of a wave
crest
lowest point of a wave
trough
amplitude of a wave
distance from the equilibrium position to a crest or a trough
NOT crest to trough
wavelength
distance from crest to crest or trough to trough
longitudinal wave
particles vibrate parallel to the direction the wave is traveling
when does the speed of a wave change
when the wave moves to another medium or when the medium’s properties are changed
energy transferred in a mechanical wave is proportional to what
square of the amplitude
damping
the amplitude of a wave gradually decreased over time as its energy is dissipated
superposition
combination of two overlapping waves
constructive interference
the resultant wave in a superposition is larger than the individual waves
when a wave is connected to a fixed boundary, what happens
waves are reflected and inverted
standing wave
wave pattern that results when two waves of the same frequency, wavelength, and amplitude travel in opposite directions and interfere
(demonstration with strobe light in class)
node
point in a standing wave that maintains no displacement
antinode
point in a standing wave that is halfway between two nodes
largest displacement occurs
periodic motion
a repeated motion
compression
region of a longitudinal wave in which the density and pressure are at a maximum
rarefaction
region of a longitudinal wave in which the density and pressure are at a minimum
what kind of waves are sound waves
longitudinal
infrasonic waves
frequencies less than 20 Hz
ultrasonic waves
frequencies above 20,000 Hz
pitch
measure of how high or low a sound is perceived
depends on the frequency of the sound wave
what happens to the pitch as the frequency rises
the pitch rises
what does the speed of a sound wave depend on
depends on how quickly one particle can transfer its motion to another particle through the medium
do sound waves travel faster though solids or gases
solids
what does speed of sound in aid depend on
temperature
Doppler effect
observed change in frequency when there is a relative motion between the source of waves and the observer
intensity
rate at which energy flows through a unit area perpendicular to the direction of wave motion
SI unit for intensity
W/m^2
watt per square meter
as the distance from the source increases, the intensity of a sound wave
decreases
same energy, larger area
loudest sound that can be tolerated by human ear
1 W/m^2
what is logarithmic in the human ear
sensation of loudness
NOT proportional to intensity
decibel
unit that describes the ratio of the two intensities of sound
resonance
the frequency of a force applied to a system matches the natural frequency of vibration of the system
fundamental frequency
lowest frequency of vibration of a standing wave
harmonic series
series of frequencies that includes the fundamental frequency and multiples of it
equation for harmonic series for vibrating string or a pipe open at both ends
includes a 2
equation for harmonic series of a pipe closed at one end
includes a 4
ONLY FOR ODD-NUMBERED HARMONICS
timbre
combination of harmonics presented at different times
pitched other than the fundamental frequency
overtones
beat
periodic variation in the amplitude of a wave that is the superposition of two waves of slightly different frequencies
number of beats per second is equal to
the frequency difference between the two sounds
at the equilibrium position, the velocity of a mass on a spring
reaches a maximum
fewest number of nodes a standing wave can have
two
a train moves down a track towards an observer. how is the sound from the train as heard by the observer different than the sound heard by a passenger on the train?
higher in pitch
Doppler effect
