“It would be possible to describe everything scientifically,
but it would make no sense; it would be without meaning,
as if you described a Beethoven symphony as a variation of
wave pressure.”
Albert Einstein
What is the difference between a vibration and a wave?
A vibration is a repeating back and forth motion about an equilibrium
position.
A wave is a vibration that propagates through space with no net
transport of matter.
In other words:
A vibration is a wiggle
in time.in time
A wave is a wiggle in both space and time.
What is a sonic boom?
Why can there be “dead spaces” in auditoriums where it is hard
to hear sound from the stage?
How much power output is there in 10 million people talking
loudly?
What is the difference between the radio wave carrying a song to
a radio and the sound of the song you hear?
Is it really possible for an opera singer’s voice to shatter glass?
How do we sense sound?
λ
The wavelength of a vibration is the distance from the top of one crest to the
top of the next. (Or, the distance between any two successive identical
parts in the graph of amplitude versus time)
The amplitude of a vibration is the distance from the midpoint to the crest (or
trough) of the graph of amplitude versus time.
xmax − xmin
A=
2
λ
Wave Motion
The period of a wave or vibration is the time for one complete vibration.
frequency = 1 / period
Wave speed = wavelength x frequency
Wave Motion
The period of a wave or vibration is the time for one complete vibration.
frequency = 1 / period
Wave speed = wavelength x frequency
Longitudinal wave: Wave in which the individual particles of a medium vibrate
back and forth in the direction in which the wave travels. (Ex: sound)
Transverse wave: Wave with vibration at right angles to the direction the wave
is traveling. (Ex: light)
When the positive peak and negative peak of two waveforms
coincide, the waves are considered to be in phase.
The amount of time by which one waveform lags the other is called
the phase shift.
The test of all knowledge is experiment. Experiment is the
sole judge of scientific “truth”
Richard Feynman
Discovery
Lab:Gharacteristics
of Vibration
Name
Group#
Date
Class
Partners
Set up a 1 kg weiohthungfroma springand usea motiondetectorand Motion
software
to plot its motion'Thedisplacement
(distance
fromequilibrium)
will executea sine
functionover time. So will the velocityand acceleration
graphs. Adjustthe coordinates
of thesegraphsso thatjusta fewoscillations
fill up the giaphswefl. Thiswiflgive
betteraccuracy.
use the graphsyouget to answerthefollowingquestions:
1. what is the periodandfrequency
of the displacement
osciflations?
2. ls the periodthe samefor the oscillations
of the velocityand acceleration
values?
3. When the displacement
(measured
fromthe equilibrium
position)is zero,whatis
happeningto the valuesof the velocityandacceleration?
Are theyzero,or at their
extremevalues,or somewhere
in-between?
4. When the displacement
fromequilibrium
is at its extremelargestvalue,whatis
happeningto the valuesof the velocityand acceleration?
5.ln general,whatis the phaserelationbetweenthe displacement
curyeandthe
velocitycurve?the acceleration
curve?(aretheyaheador behind?by how much?)
6. What is thedisplacement
amptitude?
7. What is thevelocityamplitude?
B. What is theacceleration
amplitude?
9' Look at theplotof distancevF.velocity.Whatis its shape? Whathappens
to this
graphas the amplitude
of the oscillation
decreasesovertime?
@copyright1996-2003
byDennisGilbert,do notcopywithoulpermission